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Cognitive Abilities of Araneophagic Jumping Spiders
Abstract
This chapter illustrates the cognitive abilities of araneophagic jumping spiders. “Portia,” a genus of araneophagic jumping spiders (family Salticidae), appears to have the most versatile and flexible predatory strategy known for an arthropod. A dominant feature of Portia's predatory strategy is aggressive mimicry, a system in which the predator communicates deceitfully with its prey. Typical salticids do not build webs. Instead, they are hunters that catch their prey in stalk-and-leap sequences guided by vision. Salticids differ from all other spiders by having large anteromedial eyes and acute vision. However, the behavior of Portia is anything but typical for a salticid. Besides hunting its prey cursorily, Portia also builds a prey-catching web. The typical prey of a salticid is insects, but Portia's preferred prey is other spiders. Portia frequently hunts web-building spiders from other families by invading their webs and deceiving them with aggressive-mimicry signals. While in the other spider's web, it makes aggressive-mimicry signals by moving legs, palps, abdomen, or some combination of these to make web-borne vibrations. Portia's typical victim, a web-building spider but not a salticid, typically lacks acute vision and instead perceives the world it lives in by interpreting tension and vibration patterns in its web.
... Araneophagic jumping spiders (Salticidae) adopt prey-specii c tactics for capturing other spiders (Jackson & Pollard, 1996;Jackson & Wilcox, 1998), and they prefer spiders to other prey (Li & Jackson, 1996;Li et al., 1997;Jackson, 2000;Li, 2000). Recent studies suggest that these predators are particularly relevant for research at the interface between behavioural ecology and animal cognition (Wilcox & Jackson, 1998), but the emphasis in previous studies has been on the predatory strategies of araneophagic hunters. ...
... Araneophagic jumping spiders (Salticidae) adopt prey-specii c tactics for capturing other spiders (Jackson & Pollard, 1996;Jackson & Wilcox, 1998), and they prefer spiders to other prey (Li & Jackson, 1996;Li et al., 1997;Jackson, 2000;Li, 2000). Recent studies suggest that these predators are particularly relevant for research at the interface between behavioural ecology and animal cognition (Wilcox & Jackson, 1998), but the emphasis in previous studies has been on the predatory strategies of araneophagic hunters. Here we investigate Phaeacius wanlessi Wijesinghe and Phaeacius malayensis Wanless, sit-and-wait salticids that live on the trunks of rainforest trees in Asia (Wanless, 1981;Wijesinghe, 1991) where they especially often ambush other spiders, including other salticids (Jackson & Hallas, 1986a;Jackson, 1990). ...
... The rationale for this hypothesis is the salticid's exceptional eyesight. The eyes of most spiders lack the structural complexity required for acute vision (Homann, 1928;Land, 1985), but the salticid's unique, complex eyes (Land, 1969a, b;Blest et al., 1990) give these spiders spatial acuity exceeding that known for other spiders, for insects or for any other animals of comparable size (Land, 1974;Jackson, 1998;Harland et al., 1999;Harland & Jackson, 2000;Land & Nilsson, 2002). ...
Phaeacius, a sit-and-wait jumping spider, is shown to base predatory decisions on simultaneous use of information about whether the background is matching or contrasting, whether or not the prey has good eyesight and whether the prey is oriented face on or facing away. In prey-choice testing in which mounts (dead prey in lifelike posture on a cork) were used, background and prey orientation influenced Phaeacius' behaviour specifically when a salticid came into view, salticids being prey with exceptionally good eyesight. When the prey was a non-salticid spider or an insect, Phaeacius' behaviour did not vary significantly with background or with prey orientation. In prey-reaction experiments, background and orientation influenced prey behaviour when the prey was a salticid, but not when it was a non-salticid spider or an insect. Phaeacius evidently takes special precautions to minimize the risk of being seen by a prey that has exceptional eyesight.
... Jumping spiders (Salticidae) are known for a wide array of complex behaviors (Wilcox & Jackson, 1998;Jackson & Cross, 2011;Jakob, Skow & Long, 2011). The cognitive abilities of salticids include planning, learning and reversal learning (Wilcox & Jackson, 1998;Jackson & Cross, 2011;Liedtke & Schneider, 2014) and are affected by rearing conditions (Carducci & Jakob, 2000). ...
... Jumping spiders (Salticidae) are known for a wide array of complex behaviors (Wilcox & Jackson, 1998;Jackson & Cross, 2011;Jakob, Skow & Long, 2011). The cognitive abilities of salticids include planning, learning and reversal learning (Wilcox & Jackson, 1998;Jackson & Cross, 2011;Liedtke & Schneider, 2014) and are affected by rearing conditions (Carducci & Jakob, 2000). In the jumping spider Marpissa muscosa (Clerck, 1757), different rearing environments led to differences in exploration tendency (Liedtke et al., 2015) and learning ability . ...
The central nervous system is known to be plastic in volume and structure depending on the stimuli the organism is subjected to. We tested in the jumping spider Marpissa muscosa (Clerck, 1757), whether rearing environments affect the volume of two target higher-order brain centers: the mushroom body (MB) and the arcuate body (AB). We reared female M. muscosa (N = 39) in three environments: solitarily (D: deprived), solitarily but in a physically enriched environment (P: physically enriched) and together with several siblings (G: group). We additionally investigated spiders caught from the field (W: wild). Volumes of MB and AB were compared using microCT analysis. We hypothesized that spiders reared in treatments P and G should have larger MB and AB than the spiders from treatment D, as the enriched environments are presumably cognitively more demanding than the deprived environment. Spiders from treatment P had significantly larger absolute brain volumes than spiders from treatment D, whereas brain volumes of treatment G lay in between. The relative volume of the MB was not significantly different between the treatments, whereas relative AB volumes were significantly larger in treatment P than in D, supporting the hypothesis that the AB is a center of locomotor control. W spiders had smaller absolute brain volumes and relatively smaller AB than spiders from laboratory treatments, which suggests developmental constraints under natural, possibly food-limited conditions. Additionally, differences in the relative volume of MB substructures were found. Overall, our study demonstrates that brains of jumping spiders respond plastically to environmental conditions in that absolute brain volume, as well as the relative volume of higher-order brain centers, is affected.
... Although the majority of salticids are generalist predators, the bulk of our knowledge on their hunting behaviour comes from studies of species that specialize in particularly dangerous prey: ants and spiders. These studies revealed some striking behavioural adaptations to capture such prey (LI, JACKSON 1996;TARSITANO, JACKSON 1997;WILCOX, JACKSON 1998;LI, JACKSON 2003). They also shed some light on extraordinary Unauthenticated Download Date | 12/21/15 3:53 PM cognitive abilities that enable these creatures solving complex problems. ...
... They also shed some light on extraordinary Unauthenticated Download Date | 12/21/15 3:53 PM cognitive abilities that enable these creatures solving complex problems. One particular genus, Portia from subfamily Sparteinae, has become a model in the studies of invertebrate cognition (WILCOX, JACKSON 1998;HARLAND, JACKSON 2004). ...
Predatory behaviour of Yllenus arenarius hunting flies (Diptera) was studied. The general spider's approach and capture was typical for salticids hunting prey that has high ability to escape. Two modes of approach in close proximity of prey were observed. One was typical for the majority of predatory encounters where the spider's velocity was significantly reduced with decreasing distance to prey. Stalk and movement masking were typical for this type of approach. Second mode occurred sporadically and was characterized by a high spider's velocity that was not reduced in the vicinity of the prey.
... The majority of studies have focused on salticidsspiders with exceptionally good eyesight (Harland et al. 1999;Land & Nilsson 2002) and complex, vision-guided behavior (Jackson & Pollard 1996;Harland & Jackson 2004). The studies have revealed unusual cases of versatility (Jackson 1986;Jackson & Hallas 1986;Wilcox & Jackson 1998), highly specialized strategies (Jackson & Pollard 1996;Jackson & Wilcox 1993a;Nelson et al. 2005) and cognitive feats of their miniature brains that, until recently, were thought to be distinctive only for higher vertebrates (Wilcox & Jackson 1998). Although a number of studies have demonstrated the complexity of jumping spider predatory behavior, few studies have examined how age and experience influence this behavior. ...
... The majority of studies have focused on salticidsspiders with exceptionally good eyesight (Harland et al. 1999;Land & Nilsson 2002) and complex, vision-guided behavior (Jackson & Pollard 1996;Harland & Jackson 2004). The studies have revealed unusual cases of versatility (Jackson 1986;Jackson & Hallas 1986;Wilcox & Jackson 1998), highly specialized strategies (Jackson & Pollard 1996;Jackson & Wilcox 1993a;Nelson et al. 2005) and cognitive feats of their miniature brains that, until recently, were thought to be distinctive only for higher vertebrates (Wilcox & Jackson 1998). Although a number of studies have demonstrated the complexity of jumping spider predatory behavior, few studies have examined how age and experience influence this behavior. ...
We examined differences in predatory behavior between two age groups (newly hatched spiders vs. spiders over 12 weeks old) of Yllenus arenarius Menge 1868 (Araneae: Salticidae). The spiders hunted three prey taxa (leafhoppers, caterpillars and thrips) for which they possess pre-programmed predatory behavior. The aim of the study was to check the influence of age and experience on pre-programmed predatory behavior and predatory success. Age-dependent changes occurred in four aspects of prédation: direction of approach, mode of approach, distance of attack and predatory success.
... The examples of conditional strategies expressed through behavior focus our attention on both the perceptual ability to distinguish between alternative options and the flexibility of animal behavior. Therefore the animals possessing certain limitations to their neural system are of special interest (Jackson 1992;Wilcox & Jackson 1998;Harland & Jackson 2004). Among invertebrates, conditional strategies were found in the behavior of spiders and shown to be common in salticids (Jackson 1992;Edwards & Jackson 1993, 1994Bear & Hasson 1997). ...
... The studies of mating behavior in numerous salticids revealed that the type of male courtship depends on the female's maturity and location (inside vs. outside the nest) (Jackson 1977). Predatory tactics of jumping spiders, conditioned by the prey type and location, provided even more fascinating examples of an extraordinary versatility in these arthropods (Jackson 1992;Jackson & Pollard 1996;Wilcox & Jackson 1998). ...
Generalist predators hunt a wide range of prey that possess various characteristics affecting the predators' hunting success (e.g., size, ability to detect the threat and defend against it, potential for escape). Therefore, it can be expected that the predator should flexibly react to different prey characteristics, hunting them in prey-specific ways. For a stalking predator a crucial prey feature is its ability to escape. In this study, the alternative prey-catching tactics of a dune-dwelling salticid Yllenus arenarius Menge 1868 were analyzed. Four naturally eaten prey taxa, two with a high ability to escape (Homoptera, Orthoptera) and two with a low ability to escape (Thysanoptera, larvae of Lepidoptera), were used. Numerous differences found between the tactics indicate that Y. arenarius can not only distinguish between different types of prey, but can also employ specific tactics to catch them. The tactics belong to a conditional strategy and are manifested in alternative: a) direction of approach, b) speed of approach, and c) other prey specific behaviors.
... Thus, after a detailed description of the prey behavior of the spider Portia, she claims that this behavior can be explained only if Portia is taken to be minimally conscious. As Steward puts it: "The mind module is in business" (Steward, 2012: 108; with regard to the question of animal consciousness, see also Allen & Trestman, 2023;Mendl et al., 2011;Wilcox & Jackson, 1998). ...
Merleau-Ponty’s theory of the body is often depicted as emphasizing the distinction between the physical and the conscious dimension of the body. This distinction, however, runs the risk of recreating the tension between the physical and the conscious that is at the center of the mind-body problem. In view of this, I argue for a different interpretation of Merleau-Ponty, according to which his theory of the body is an attempt to establish “the union of the soul and the body” (Merleau-Ponty, 2012: 91, 99) by way of an analysis of the phenomenon of being in the world. This phenomenon does not just go beyond reflective but also beyond pre-reflective consciousness. It is an essential feature of living beings that has a teleological structure and that stands in the way of a reduction of living beings to physical objects. In the end, Merleau-Ponty argues for an antireductionist and metaphysically quite charged concept of life that is supposed to bridge the gap between the conscious and the organic dimension of human existence and that holds important insights for the contemporary debates on minimal consciousness, the life-mind continuity, autopoietic enactivism, and causation.
... Another intriguing example is the spitting spider, Scytodes pallida Doleschall, which regulated the amount of spit depending on the size of prey and its struggling intensity (Clements & Li, 2005). Portia spiders have capacities (Wilcox & Jackson, 1998) to use alternative capture strategies, with or without the use of a web (Jackson & Hallas, 1986). Such switching foraging behaviour remains little known in other generalist spider predators. ...
Generalist predators have evolved a variety of behavioural adaptations in prey capture to effectively subdue different prey types. Such predators use a conditional hunting strategy. Among spiders, representatives of Gnaphosidae are known to use either venom attack (subduing prey with venom) or silk attack (subduing prey with silk). In this study, we aimed to test the hypothesis of the conditional use of prey capture strategy (venom versus silk attack) in two species, Drassodes sp. and Zelotes sp. We also measured the size of their venom glands and the number of their piriform glands in order to reveal whether behavioural adaptations are paralleled with morphological ones. As prey, we used other spiders of variable sizes as these are considered dangerous prey. We found that Drassodes used mainly silk attack, while the majority of Zelotes used venom attack. The probability of using silk attack increased with predator/prey body length ratio in Drassodes, but not in Zelotes. Then, we disabled silk use in individuals of both species. All disabled Drassodes used venom attack, but about half of individuals attempted to use silk attack first. All Zelotes used venom attack, and none attempted to use silk attack first. We found significantly larger venom glands in Drassodes than in Zelotes, while the number of piriform silk glands was similar. The behavioural adaptations are, thus, not paralleled with morphological (i.e., venom and silk gland size) ones. Our results suggest that both Drassodes and Zelotes can use both attack strategies with similar efficacy. Generalist ground spider predators use either venom or silk attack to immobilize their prey. We show that after disabling spinnerets, the spiders switched to the venom attack. We found that venom or silk attack is not paralleled with size of venom and silk glands. Photos: R. Macek.
... Many have viewed arachnid behavior as being governed by instinct (Jackson and Cross 2011;Jakob et al. 2011). However, investigations hint that this is not always the case (Wilcox and Jackson 1998;Herberstein et al. 2013;Peckmezian and Taylor 2015). To what degree social living promotes greater or reduced cognitive ability, discussed above as the social brain and distributed cognition hypotheses Perez-Barberia et al. 2007), and how this impacts collective learning in social arachnids, is unknown. ...
Collective personalities refer to temporally consistent behavioral differences between distinct social groups. This phenomenon is a ubiquitous and key feature of social groups in nature, as virtually every study conducted to date has documented repeatable between-group differences in collective behavior, and has revealed ongoing selection on these traits in both the laboratory and field environments. Five years ago, foundational reviews by Bengston and Jandt pioneered this topic and delimited the present knowledge on collective personality. Here, we update these reviews by summarizing the recent works conducted in the field’s most prominent model systems: social spiders and eusocial insects. After presenting how these recent works helped scientists to better understand the determinants of collective personality, we used a trait-by-trait format to compare and contrast the results and thematic trends obtained in these taxa on 10 major aspects of collective personality: division of labor, foraging, exploration, boldness, defensive behavior, aggressiveness, decision-making, cognition, learning, and nest construction. We then discuss why similarities and dissimilarities in these results open the door to applying numerous theories developed in evolutionary behavioral ecology for individual traits (e.g., life history theory, game theory, optimal foraging theory) at the colony level, and close by providing examples of unexamined questions in this field that are ripe for new inquiries. We conclude that collective personality, as a framework, has the potential to improve our general understanding of how selection acts on intraspecific variation in collective phenotypes that are of key importance across arthropod societies and beyond.
... However, while octopuses are invertebrates, they possess problem-solving abilities and an awareness of their bodies, which would suggest a high level of cognitive functioning (Ikeda, 2009). Portia spiders, which prey on other spiders, are able to mimic the vibrations made by the insects that their prey spiders eat to trick them into approaching them (Wilcox and Jackson, 1998). Bees are able to solve the "traveling salesman's dilemma," understanding the most efficient route between three, four, or more different places and expressing that route to other bees through a "waggle dance" (Wong et al., 2008). ...
Animals have been used for centuries in scientific studies. These have resulted in many benefits to humans and other animals, such as blood pressure medications and the flu vaccine for humans, and hip replacement surgeries and vaccines against painful, debilitating illnesses for animals. The advantages of laboratory animal research are a very high level of environmental and genetic control. Moreover, at the present time, humans sanction the use of invasive and lethal research methods in animals; this places human interests over the rights of animals and may also compromise the individual animal’s welfare. The Three Rs (replacement, reduction, and refinement) provide guidelines for the ethical use of animals in science and may be used to guide and potentially improve laboratory animal welfare. Observational studies of animals in their natural habitat, or use of pet animals, can help reduce welfare concerns, but they also reduce the environmental and genetic control. Service and therapy animals may provide benefits to people whom they assist; however, limitations to the quality of science used to evaluate such benefits do not yet enable conclusions to be drawn.
... The bugs were more prone to break threads in the presence of wind, and all measured components of thread-breaking behaviour were faster when there was wind present. This suggests that the bugs are taking advantage of wind to mask their behaviour, because wind can temporarily impair the spiders' ability to detect web-borne vibrations [26,27]. Estimates of spider responses elicited by thread-breaking behaviour range from 14% in this study (see the electronic supplementary material, S2) to 56% [20]; the latter should be regarded as an overestimate as it considered 'thread-breaking sequences' that entail breaking of single threads or breaking of several consecutive threads. ...
Some predators sidestep environments that render them conspicuous to the sensory systems of prey. However, these challenging environments are unavoidable for certain predators. Stenolemus giraffa is an assassin bug that feeds on web-building spiders; the web is the environment in which this predator finds its prey, but it also forms part of its preys’ sophisticated sensory apparatus, blurring the distinction between environment and sensory systems. Stenolemus giraffa needs to break threads in the web that obstruct its path to the spiders, and such vibrations can alert the spiders. Using laser vibrometry, this study demonstrates how S. giraffa avoids alerting the spiders during its approach.When breaking threads, S. giraffa attenuates the vibrations produced by holding on to the loose ends of the broken thread and causing them to sag prior to release. In addition, S. giraffa releases the loose ends of a broken thread one at a time (after several seconds or minutes) and in this way spaces out the production of vibrations in time. Furthermore, S. giraffa was found to maximally reduce the amplitude of vibrations when breaking threads that are prone to produce louder vibrations. Finally, S. giraffa preferred to break threads in the presence of wind, suggesting that this araneophagic insect exploits environmental noise that temporarily impairs the spiders’ ability to detect vibrations. The predatory behaviour of S. giraffa seems to be adaptated in intricate manner for bypassing the sophisticated sensory systems of web-building spiders. These findings illustrate how the physical characteristics of the environment, along with the sensory systems of prey can shape the predatory strategies of animals.
... In spiders, the pioneering work of Robert Jackson and his colleagues revealing surprisingly complex problem-solving capabilities in jumping spiders (e.g. Tarsitano & Jackson 1997;Wilcox & Jackson 1998) helped inspire arachnologists to focus on learning and other cognitive processes (see reviews in Cross & Jackson 2006;Jackson & Cross 2011;Jakob et al. 2011). ...
Spiders are capable of learning in many different contexts, including prey capture, social interactions and predator avoidance. In recent years, there has been an upturn in the number of published studies of learning in spiders, with a particular interest in active hunters that do not build prey-capture webs. However, as is often the case when developing protocols for studying learning in a new taxonomic group, many researchers have tested methods that failed to produce interpretable results. These methods largely remain unpublished, although knowing what has already been attempted would be of great benefit to the community of researchers that work on arthropod learning. Here, we briefly review published methods that have been successful in demonstrating learning in actively hunting spiders, as well as report on unpublished, unsuccessful methods that we collected from the research community.
... Recent work on neural network modeling has shown that it is possible to reproduce associative learning, as well as other cognitive abilities, with the relatively small number of neurons found in insect brains (see Chittka and Niven, 2009, for a review). Wilcox and Jackson (1998) have already demonstrated remarkable cognitive behavior in jumping spiders. This is the first report of learning in the order Opiliones. ...
... Soley, personal communication). Something similar is also observed in the choppy walking gait of Portia salticids in webs (Jackson & Blest 1982;Wilcox & Jackson 1998). An interesting parallel also occurs in grasshoppers that are able to walk with a vibratory signature that resembles wind vibrations, enabling them to walk undetected near cursorial Cupiennius spiders (Barth et al. 1988). ...
Predatory arthropods that specialize in invading webs and preying on the resident spiders ('araneophagic predators') face special challenges. As webs are exceedingly good at transmitting vibrations, it is difficult for a web invader to move through the web and remain undetected by the spider. An araneophagic predator that generates vibrations in the web may risk prey escaping or even counterattacking. To increase the chances of an undetected approach, predators may exploit episodes of environmental noise to approach, while their prey's ability to detect them is compromised ('opportunistic smokescreen behaviour'). Here we provide the first experimental evidence of convergent opportunistic smokescreen behaviour in an araneophagic insect, Stenolemus bituberus Stal (Reduviidae), which preys on web-building spiders. We tested how two common types of environmental noise, wind and localized vibrations in the web, influence the predatory behaviour and success of assassin bugs when hunting spiders. We found that assassin bugs were more likely to catch the spider in the presence of wind. During episodes of environmental noise, assassin bugs stepped more often and walked in a more continuous manner, apparently exploiting the opportunity to approach while the prey's sensory system is less able to detect the predator. Changes in predatory behaviour in the presence of environmental noise were not evident when S. bituberus was in an unoccupied spider web. This supports our hypothesis that noise-related timing of behaviour reflects decisions made as part of a predatory strategy, rather than responses to physical disturbance.
... The studies of salticid behavior reveal examples of extraordinary cognitive abilities of these small invertebrates with very small neural systems. A well-studied example includes spiders from the genus Portia Karsch 1878, these are gradually becoming models in the study of invertebrate cognition (Wilcox & Jackson 1998;Harland & Jackson 2004). They are able to invade alien webs, generating variable aggressive-mimicry signals (Jackson & Wilcox 1993a), orusing opportunistic smokescreen behaviors -approach the spider host without being noticed (Wilcox et al. 1996). ...
The hunting behavior of juvenile Yllenus arenarius Menge 1868 in their first week after leaving sub-sand nests was studied. The spiders were tested with prey that can effectively escape (Homoptera) and prey that are not capable of efficient escape (Thysanoptera and larvae of Lepidoptera) in order to assess the complexity of young spider's hunting tactics. Numerous differences were found in the mode of catching the prey, which indicate that the spiders possess a conditional hunting strategy. The strategy is expressed in direction of approach, speed of approach, distance of attack and other prey-specific behaviors. The results strongly suggest the pre-programmed background of both the observed behaviors and sensitivity towards certain prey characteristics that enabled prey identification.
... Besides stalking prey away from webs, these remarkable salticids build their own prey-capture webs and also make predatory raids into other spiders' webs where they take insects, the resident spider and its eggs. Spiders in alien webs are not simply stalked or chased down, but instead deceived and manipulated by aggressive mimicry signals (Wilcox & Jackson, 1998). ...
Portia fimbriata from Queensland, Australia, is an araneophagic jumping spider (Salticidae) that includes in its predatory strategy a tactic (cryptic stalking) enabling it to prey effectively on common sympatric salticids from other genera. Using standardized tests in which only optical cues were available (prey enclosed in small glass vial within large cage), the reactions of P. fimbriata to 114 salticid species were investigated. Except for Myrmarachne spp. (ant mimics), all salticids tested triggered cryptic stalking by P. fimbriata. This included not only sympatric, but also allopatric, salticids. The salticid on which P. fimbriata most commonly preys in nature is Jacksonoides queenslandicus, but cryptic stalking was triggered by salticid species with considerably different appearances, including beetle mimics, species with unusual body shapes and species with a wide variety of camouflaging markings. Portia fimbriata was also tested with lycosid, clubionid, theridiid and desid spiders and with flies and ants, but none of these arthropods triggered cryptic stalking. Optical cues used by P. fimbriata for discrimination between salticid and non-salticid prey are discussed.
In investigating convergent minds, we need to be sure that the things we are looking at are both minds and convergent. In determining whether a shared character state represents a convergence between two organisms, we must know the wider distribution and primitive state of that character so that we can map that character and its state transitions onto a phylogenetic tree. When we do this, some apparently primitive shared traits may prove to represent convergent losses of cognitive capacities. To avoid having to talk about the minds of plants and paramecia, we need to go beyond assessments of behaviourally defined cognition to ask questions about mind in the primary sense of the word, defined by the presence of mental events and consciousness. These phenomena depend upon the possession of brains of adequate size and centralized ontogeny and organization. They are probably limited to vertebrates. Recent discoveries suggest that consciousness is adaptively valuable as a late error-detection mechanism in the initiation of action, and point to experimental techniques for assessing its presence or absence in non-human mammals. © 2017 The Author(s) Published by the Royal Society. All rights reserved.
Jumping spiders are known for their extraordinary cognitive abilities. The underlying nervous system structures, however, are largely unknown. Here, we explore and describe the anatomy of the brain in the jumping spider Marpissa muscosa (Clerck, 1757) by means of paraffin histology, X-ray microCT analysis and immunohistochemistry as well as three-dimensional reconstruction. In the prosoma, the CNS is a clearly demarcated mass that surrounds the esophagus. The anteriormost neuromere, the protocerebrum, comprises nine bilaterally paired neuropils, including the mushroom bodies and one unpaired midline neuropil, the arcuate body. Further ventrally, the synganglion comprises the cheliceral (deutocerebrum) and pedipalpal neuropils (tritocerebrum). Synapsin-immunoreactivity in all neuropils is generally strong, while allatostatin-immunoreactivity is mostly present in association with the arcuate body and the stomodeal bridge. The most prominent neuropils in the spider brain, the mushroom bodies and the arcuate body, were suggested to be higher integrating centers of the arthropod brain. The mushroom body in M. muscosa is connected to first and second order visual neuropils of the lateral eyes, and the arcuate body to the second order neuropils of the anterior median eyes (primary eyes) through a visual tract. The connection of both, visual neuropils and eyes and arcuate body, as well as their large size corroborates the hypothesis that these neuropils play an important role in cognition and locomotion control of jumping spiders. In addition, we show that the architecture of the brain of M. muscosa and some previously investigated salticids differs significantly from that of the wandering spider Cupiennius salei, especially with regard to structure and arrangement of visual neuropils and mushroom body. Thus, we need to explore the anatomical conformities and specificities of the brains of different spider taxa in order to understand evolutionary transformations of the arthropod brain.
This book presents a study of what it is for individuals to represent the physical world with the most primitive sort of objectivity. By reflecting on the science of perception and related psychological and biological sciences, it gives an account of constitutive conditions for perceiving the physical world, and thus aims to locate origins of representational mind. The book illuminates several long-standing, central issues in philosophy, and provides a wide-ranging account of relations between human and animal psychologies.
Sentience - the ability to feel, perceive and experience - is central to the animal welfare debate as it raises the question of whether animals experience suffering in life and death. This book explores and answers these questions in an objective way, based on the latest research and empirical evidence. Beginning with an introduction to sentience, the book investigates why we are so interested in sentience, when, as a species, humans became sentient and how it has changed over time. The book defines aspects of sentience such as consciousness, memory and emotions, and discusses brain complexity in detail. Looking at sentience from a developmental perspective, it analyses when in an individual's growth sentience can be said to appear and uses evidence from a range of studies investigating embryos, foetuses and young animals to form an enlightening overview of the subject. With a full chapter covering ethical decisions such as animal protection and experimentation, this book is not only an invaluable resource for researchers and students of animal welfare and biology, but also an engaging and informative read for veterinarians and the general public.
Considering the fear that spiders can generate in humans, examining human–spider interactions in urban settings may at first glance appear odd. However, human–spider interactions, which occur quite frequently in urban settings, do not necessarily have to be negative; they can, in some cases, foster respect and tolerance (sometimes through avoidance). When one considers how global transformations, invasive species, urbanization, and adaptation will impact human–spider interactions, a review of the literature pertaining to these encounters is timely. We begin this discussion by describing spiders and providing an overview of some of their positive and negative impacts. Challenges regarding species identification and envenoming are also discussed. After the role of biological, psychological, and social aspects in human–spider interactions are re-examined, we provide future options aimed at organizing broad-scale public programs for five specific target groups: 1) the general public, 2) health professionals, 3) educators, 4) naturalists, and 5) researchers. In the conclusion, we provide potential management and educational strategies aimed at increasing our knowledge and tolerance of these animals in urban settings.
Gottlieb's developmental psychobiology book provides a base for reexamining the place of the experimental analysis of behavior in the life sciences. His experimental program demonstrating the critical function of the environment in the development of a species-typical behavior helped force an acceptance of probabilistic epigenesis, the acknowledgment that the developmental genome-environment system is fully interactional. (Indeed, nature vs. nurture is deader than a doornail.) The repercussions for evolutionary biology and the roles and categorizations of genes, behavior, and environment in behavior-environment relations are explored in light of current knowledge, including specific implications for the experimental analysis of behavior.
Spiders are highly efficient predators in possession of exquisite sensory capacities for ambushing prey, combined with machinery for launching rapid and determined attacks. As a consequence, any sexually motivated approach carries a risk of ending up as prey rather than as a mate. Sexual selection has shaped courtship to effectively communicate the presence, identity, motivation and/or quality of potential mates, which help ameliorate these risks. Spiders communicate this information via several sensory channels, including mechanical (e.g. vibrational), visual and/or chemical, with examples of multimodal signalling beginning to emerge in the literature. The diverse environments that spiders inhabit have further shaped courtship content and form. While our understanding of spider neurobiology remains in its infancy, recent studies are highlighting the unique and considerable capacities of spiders to process and respond to complex sexual signals. As a result, the dangerous mating systems of spiders are providing important insights into how ecology shapes the evolution of communication systems, with future work offering the potential to link this complex communication with its neural processes.
Cognitive Ethology, the field initiated by Donald R Griffin, was defined by him as the study of the mental experiences of animals as they behave in their natural environment in the course of their normal lives. It encompasses both the problems defined by Chalmers as the ‘hard’ problem of consciousness, phenomenological experience, and the ‘easy’ problems, the phenomena that appear to be explicable (someday) in terms of computational or neural mechanisms. Sources for evidence of consciousness and other mental experiences that Griffin suggested and are updated here include (1) possible neural correlates of consciousness, (2) versatility in meeting novel challenges, and (3) animal communication which he saw as a potential ‘window’ into their mental experiences. Also included is a very brief discussion of pertinent philosophical and conceptual issues; cross-species neural substrates underlying selected cognitive abilities; memory capacities especially as related to remembering the past and planning for the future; problem solving, tool use and strategic behavioral sequences such as those needed in anti-predator behaviors. The capacity for mirror self-recognition is examined as a means to investigate higher levels of consciousness. The evolutionary basis for morality is discussed. Throughout are noted the admonitions of von Uexküll to the scientist to attempt to understand the Umwelt of each animal. The evolutionary and ecological impacts and constraints on animal capacity and behavior are examined as possible. WIREs Cogn Sci 2013, 4:493–509. doi: 10.1002/wcs.1239
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Conflict of interest: The author has declared no conflicts of interest for this article.
Spiders, having minute brains, were once considered simple, instinct-driven automatons, but research on spider biology is revealing increasing evidence of their cognitive abilities. In this review, we discuss the complex, flexible behaviour of spiders, especially salticids, and highlight how sometimes the cognitive character of spider behaviour closely parallels that of much bigger animals. This includes the use of selective attention (both visual and olfactory) and the use of planned detours. The implications of these findings, and how they relate to bigger issues traditionally associated with big-brain animals, such as ‘representation’ and ‘mind’, are discussed. Also discussed are issues relating to animals, including spiders, having a preference, instead of a search image, for a particular type of prey, and issues relating to spiders classifying different types of prey. Some of these issues are illustrated by exploring how spiders communicate and play mind games with their prey, as well as with potential mates. We also discuss how much about cognition can be revealed by exploring the perceptual systems of spiders.
Brettus adonis, Brettus albolimbatus, Cyrba algerina, Cyrba ocellata, and Cyrba simoni are spartaeine jumping spiders (Salticidae) that invade other spiders’ webs, make vibratory signals that deceive the resident spider (aggressive mimicry), then attack and eat the spider. The signal‐generation behaviour of each of these five species is investigated in the laboratory. Each species is characterised by flexible predatory behaviour, including use of a trial‐and‐error (generate‐and‐test) algorithm to derive appropriate aggressive‐mimicry signals: first broadcast an array of different signals, then choose particular signals as a consequence of feedback from the prey spider. However, in laboratory experiments, B. adonis and B. albolimbatus relied on trial‐and‐error significantly more often than did C. algerina, C. ocellata, and C. simoni. Maternal effects and variation in experience were minimised because all individuals tested were laboratory‐reared to the second and third generation under standardised conditions. Selection pressures that may have been responsible for evolution of different levels of flexibility are considered.
There are several types of behavioural evidence in favour of the notion that many animal species experience at least some simple levels of consciousness. Other than behavioural evidence, there are a number of anatomical and physiological criteria that help resolve the problem of animal consciousness, particularly when addressing the problem in lower vertebrates and invertebrates. In this paper, I review a number of such behavioural and brain- based evidence in the case of mammals, birds, and some invertebrate species. Cumulative evidence strongly suggests that consciousness, of one form or another, is present in mammals and birds. Although supportive evidence is less strong in the case of invertebrates, it is more likely than not that they also experience some simple levels of consciousness.
Portia is a genus of web-invading araneophagic jumping spiders known from earlier studies to derive aggressive-mimicry signals by using a generate-and-test algorithm (trial-and-error tactic). Here P. fimbriata's use of trial-and-error to solve a confinement problem (how to escape from an island surrounded by water) is investigated. Spiders choose between two potential escape tactics (leap or swim), one of which will fail (bring spider no closer to edge of tray) and the other of which will partially succeed (bring spider closer to edge of tray). The particular choice that will partially succeed is unknown to the spider. Using trial-anderror, P.fimbriata solves the confinement problem both when correct choices are rewarded (i.e. when the spider is moved closer to edge of tray) and when incorrect choices are punished (i.e. when the spider gets no closer to edge of tray).
The lifespan of Y. arenarius is about 720 days for males and 750 days for females (maximum 770 days), which makes it the longest lived salticid reported from natural conditions. The juvenile spiders emerge at the beginning of June and mature not before the following August. They mate in autumn and hibernate for the second time. For most of the year two cohorts coexist, and at the beginning of June three cohorts can be found simultaneously. The life cycle suggests that in the studied areas there are two groups of individuals, the first of which produces young in odd years, while the other group reproduces in even years. The spider lifespan and phenology suggest no or limited gene flow between the groups.
Portia fimbriata is a web-invading araneophagic jumping spider (Salticidae). The use of signal-generating behaviours is characteristic of how P. fimbriata captures its prey, with three basic categories of signal-generating behaviours being prevalent when the prey spider is in an orb web. The predatory behaviour of P. fimbriata has been referred to as aggressive mimicry, but no previous studies have provided details concerning the characteristics of P. fimbriata's signals. We attempt to determine the model signals for P. fimbriata's ‘aggressive mimicry’ signals. Using laser Doppler vibrometer and the orb webs of Zygiella x-notata and Zosis geniculatus, P. fimbriata's signals are compared with signals from other sources. Each of P. fimbriata's three categories of behaviour makes a signal that resembles one of three signals from other sources: prey of the web spider (insects) ensnared in the capture zone of the web, prey making faint contact with the periphery of the web and large-scale disturbance of the web (jarring the spider's cage). Experimental evidence from testing P. fimbriata with two sizes of lure made from Zosis (dead, mounted in a lifelike posture in standard-size orb web) clarifies P. fimbriata's signal-use strategy: (1) when the resident spider is small, begin by simulating signals from an insect ensnared in the capture zone (attempt to lure in the resident spider); (2) when the resident spider is large, start by simulating signals from an insect brushing against the periphery of the web (keep the resident spider out in the web, but avoid provoking from it a full-scale predatory attack); (3) when walking in the resident spider's web, regardless of the resident spider's size, step toward the spider while making a signal that simulates a large-scale disturbance of the web (mask footsteps with a self-made vibratory smokescreen).
Signal-generation behavior of Portia labiata, a web-invading araneophagic jumping spider (Salticidae), was investigated in the laboratory. Individuals derived from two habitats in the Philippines were compared: Los Baos, a low-elevation tropical rainforest site where prey (spider) diversity is especially high, and Sagada, a high-elevation pine-forest site where prey (spider) diversity is less. Maternal effects and variation in experience were minimized because all individuals tested were from laboratory rearing to second and third generation under standardized conditions. Individuals from both populations used a trial-and-error (generate-and-test) algorithm to derive appropriate aggressive-mimicry signals. However, in laboratory experiments, the Los Baos P. labiata relied on trial and error significantly more often than did the Sagada P. labiata. Selection pressures that may have been responsible for evolution of different levels of flexibility are considered, including the different arrays of prey to which the Los Baos and the Sagada P. labiata are exposed.
This paper argues that navigating insects and spiders possess a degree of mindedness that makes them appropriate (in the sense
of “possible”) objects of sympathy and moral concern. For the evidence suggests that many invertebrates possess a belief-desire-planning
psychology that is in basic respects similar to our own. The challenge for ethical theory is find some principled way of demonstrating
that individual insects do not make moral claims on us, given the widely held belief that some other “higher” animals do make such claims on us.
The jumping spider Portia labiata can complete detours in which it must move away from a goal (i.e. prey) before approaching it. This detouring behaviour can be divided into two phases: a scanning phase, during which Portia stays roughly in one spot and examines its environment using its principal eyes, and a locomotory phase, during which Portia performs the detour. Earlier experiments showed that when Portia is initially confined to a small, elevated platform from which it has an unobstructed view of the goal, it plans the initial stage of its detour by scanning the possible route and picking out an unbroken path from start to goal and then aiming at an initial objective along the detour. In the present experiments, I examined the detouring behaviour of P. labiata in an open arena where obstacles provided either indirect access or no access to the goal. Although scanning movements and detour decisions of spiders were similar to those of spiders initially confined to an elevated platform, spiders in the open arena not only scanned at the start but also along the route of the detour. Decision making thus occurred gradually, during both the scanning and the locomotory phases. Taken together, these results and those of previous studies suggest that detouring behaviour in Portia involves a form of vicarious trial and error in which the spider inspects possible routes and selects a series of intermediate goals during both the scanning and locomotory phases of a detour.
Vibrational signalling is a widespread form of animal communication and, in the form of sexual communication, has been generally regarded as inherently short-range and a private communication channel, free from eavesdropping by generalist predators. A combination of fieldwork and laboratory experiments was used to test the hypothesis that predators can intercept and exploit such signals. First, we developed and characterized PCR primers specific for leafhoppers of the genus Aphrodes and specifically for the species Aphrodes makarovi. Spiders were collected from sites where leafhoppers were present and screened with these primers to establish which spider species were significant predators of this species during the mating period of these leafhoppers. Analysis using PCR of the gut contents of tangle-web spiders, Enoplognatha ovata (Theridiidae), showed that they consume leafhoppers in the field at a greater rate when signalling adults were present than when nymphs were dominant, suggesting that the spiders were using these vibrations signals to find their prey. Playback and microcosm experiments then showed that E. ovata can use the vibrational signals of male leafhoppers as a cue during foraging and, as a result, killed significantly more male than female A. makarovi. Our results show, for the first time, that arthropod predators can exploit prey vibrational communication to obtain information about prey availability and use this information to locate and capture prey. This may be a widespread mechanism for prey location, one that is likely to be a major unrecognized driver of evolution in both predators and prey.
Little is known about how a prey species' cognitive limitations might shape a predator's prey-capture strategy. A specific hypothesis is investigated: predators take advantage of times when the prey's attention is focussed on its own prey. Portia fimbriata, an araneophagic jumping spider (Salticidae) from Queensland, is shown in a series of 11 experiments to exploit opportunistically a situation in which a web-building spider on which it preys, Zosis genicularis (Uloboridae), is preoccupied with wrapping up its own prey. Experimental evidence supports three conclusions: (1). while relying on optical cues alone, P. fimbriata perceives when Z. genicularis is wrapping up prey; (2). when busy wrapping up prey, the responsiveness of Z. genicularis to cues from potential predators is diminished; and (3). P. fimbriata moves primarily during intervals when Z. genicularis is busy wrapping up prey. P. fimbriata's strategy is effective partly because the wrapping behaviour of Z. genicularis masks the web signals generated by the advancing P. fimbriata's footsteps and also because, while wrapping, Z. genicularis' attention is diverted away from predator-revealing cues.
The extent to which decision-making processes are constrained in animals with small brains is poorly understood. Arthropods have brains much smaller and simpler than those of birds and mammals. This raises questions concerning limitations on how intricate the decision-making processes might be in arthropods. At Los Baños in the Philippines, Scytodes pallidus is a spitting spider that specialises in preying on jumping spiders, and Portia labiata is a jumping spider that preys on S. pallidus. Scytodid spit comes from the mouth, and egg-carrying females are less dangerous than eggless scytodids because the female uses her chelicerae to hold her eggs. Held eggs block her mouth, and she has to release them before she can spit. The Los Baños P. labiata sometimes adjusts its tactics depending on whether the scytodid encountered is carrying eggs or not. When pursuing eggless scytodids, the Los Baños P. labiata usually takes detour routes that enable it to close in from behind (away from the scytodid's line of fire). However, when pursuing egg-carrying scytodids, the Los Baños P. labiata sometimes takes faster direct routes to reach these safer prey. The Los Baños P. labiata apparently makes risk-related adjustments specific to whether scytodids are carrying eggs, but P. labiata from Sagada in the Philippines (allopatric to Scytodes) fails to make comparable risk-related adjustments.
This paper reviews evidence that increases the probability that many animals experience at least simple levels of consciousness. First, the search for neural correlates of consciousness has not found any consciousness-producing structure or process that is limited to human brains. Second, appropriate responses to novel challenges for which the animal has not been prepared by genetic programming or previous experience provide suggestive evidence of animal consciousness because such versatility is most effectively organized by conscious thinking. For example, certain types of classical conditioning require awareness of the learned contingency in human subjects, suggesting comparable awareness in similarly conditioned animals. Other significant examples of versatile behavior suggestive of conscious thinking are scrub jays that exhibit all the objective attributes of episodic memory, evidence that monkeys sometimes know what they know, creative tool-making by crows, and recent interpretation of goal-directed behavior of rats as requiring simple nonreflexive consciousness. Third, animal communication often reports subjective experiences. Apes have demonstrated increased ability to use gestures or keyboard symbols to make requests and answer questions; and parrots have refined their ability to use the imitation of human words to ask for things they want and answer moderately complex questions. New data have demonstrated increased flexibility in the gestural communication of swarming honey bees that leads to vitally important group decisions as to which cavity a swarm should select as its new home. Although no single piece of evidence provides absolute proof of consciousness, this accumulation of strongly suggestive evidence increases significantly the likelihood that some animals experience at least simple conscious thoughts and feelings. The next challenge for cognitive ethologists is to investigate for particular animals the content of their awareness and what life is actually like, for them.
An experimental study of search-image use by araneophagic jumping spiders (i.e., salticid spiders that prey routinely on other spiders) supports five conclusions. First, araneophagic salticids have an innate predisposition to form search images for specific prey from their preferred prey category (spiders) rather than for prey from a non-preferred category (insects). Second, single encounters are sufficient for forming search images. Third, search images are based on selective attention specifically to optical cues. Fourth, there are trade-offs in attention during search-image use (i.e., forming a search image for one type of spider diminishes the araneophagic salticid's attention to other spiders). Fifth, the araneophagic salticid's adoption of search images is costly to the prey (i.e., when the araneophagic salticid adopts a search, the prey's prospects for surviving encounters with the araneophagic salticid are diminished). Cognitive and ecological implications of search-image use are discussed.
Most early studies of consciousness have focused on human subjects. This is understandable, given that humans are capable of reporting accurately the events they experience through language or by way of other kinds of voluntary response. As researchers turn their attention to other animals, "accurate report" methodologies become increasingly difficult to apply. Alternative strategies for amassing evidence for consciousness in non-human species include searching for evolutionary homologies in anatomical substrates and measurement of physiological correlates of conscious states. In addition, creative means must be developed for eliciting behaviors consistent with consciousness. In this paper, we explore whether necessary conditions for consciousness can be established for species as disparate as birds and cephalopods. We conclude that a strong case can be made for avian species and that the case for cephalopods remains open. Nonetheless, a consistent effort should yield new means for interpreting animal behavior.
The production of multimodal signals during animal displays is extremely common, and the function of such complex signaling has received much attention. Currently, the most frequently explored hypotheses regarding the evolution and function of complex signaling focus on the signal and/or signaler, or the signaling environment, while much less attention has been placed on the receivers. However, recent studies using vertebrates suggest that receiver psychology (e.g. learning and memory) may play a large role in the evolution of complex signaling. To date, the influence of multimodal cues on receiver learning and/or memory has not been studied in invertebrates. Here, we test the hypothesis that the presence of a seismic (vibratory) stimulus improves color discrimination learning in the jumping spider Habronattus dossenus. Using a heat-aversion learning experiment, we found evidence for a cross-modal effect on color learning. Over a series of training trials, individuals exposed to a seismic stimulus jumped onto the heated color less frequently and remained there for less time than did individuals not exposed to a seismic stimulus. In addition, in a final no-heat test trial, individuals from the seismic-present treatment were more likely to avoid the previously heated color than were individuals from the seismic-absent treatment. This is the first study to demonstrate a cross-modal influence on learning in an invertebrate.
In 1966, the comparative psychologist T. C. Schneirla wrote that “behavioral ontogenesis is the backbone of comparative psychology” (p. 284). An accurate comprehension of other aspects of behavior (e.g., behavioral evolution, behavioral genetics, and social psychology) depends on understanding how behavior develops within the individual organism. According to Schneirla, shortcomings in the study of behavioral development will inevitably handicap other lines of investigation. Thus, if Schneirla was correct (and I shall adopt the position that he was), we must appreciate how behavior develops and must also be able to assess the soundness of the developmental data base, both conceptually and methodologically.
Some of the best minds in learning theory circa 1930–1950 dealt with problems involving spatial orientation in animals. In the ensuing Skinner era of the ’50s and ’60s, spatial problems were mostly ignored while attention was focused on reinforcement schedules and repetitive manipulative behavior. Late in the 1960s, however, learning researchers began returning to spatial problems, as did others whose interests lay in memory, reasoning and the neural mechanisms of behavior. Today, the ambience in parts of the field is strongly evocative of the 1930s. Problems, apparatuses and theoretical languages that were in vogue half a century ago appear in the current literature once again, and spatial behavior figures prominently in this trend.
Jumping spiders of the genus Phidippus tend to occupy waiting positions on plants during the day. From such reconnaissance positions, the spiders often utilize an indirect route of access (detour) to attain a position from which sighted prey (the primary objective of pursuit) can be captured.
Selection of an appropriate route of access is based upon movement toward a visually determined secondary objective (part of a plant) which may provide access to the prey position (Fig. 2, Table 1).
During pursuit, the spider retains a memory of the relative position of the prey at all times. This memory of prey position is frequently expressed in the form of a reorientation turn to face the expected position of the prey (Fig. 1). Each reorientation can be considered to initiate a new segment of the pursuit.
Phidippus employ the immediate direction (or route) of pursuit as a reference direction, for the determination of prey position (Figs. 3 and 4). The spider compensates for its own movement in determining the direction of the prey from a new position (Fig. 5).
The spider retains a memory of the prey direction with reference to gravity (Fig. 6); this memory of the inclination of prey direction can take precedence over conflicting information based upon the use of the route as a reference direction (Figs. 7 and 8).
Visual cues provided by both the background and the immediate plant configuration can be used by the spider to determine a (radial) direction in the plane perpendicular to the route of pursuit (Fig. 9, Table 2).
The jumping spider must employ at least two independent reference systems (route direction, gravity, visual cues) in concert to determine the position of the prey in space (Fig. 10 and Table 3, Fig. 11).
Apart from the context of predatory pursuit, the indirect pursuit of visually determined objectives is a general feature of the movement of salticid spiders upon vegetation.
Taieria erebus (Gnaphosidae) was found to be a versatile predator: it captured insects both cursorially (away from webs) and kleptopar-asitically (on alien webs); it captured spiders in both the presence and absence of webs; and it also ate the eggs of host spiders (oophagy). When T. erebus invaded webs, it was as an aggressive mimic — it performed a repertoire of vibratory behaviours to lure the host spider. Although T. erebus pursued and captured spiders on diverse web-types, it was more effective as a predator when invading densely (rather than sparsely) woven cribellate and non-sticky webs, and was especially effective on non-cribellate sticky webs. Gnaphosids are traditionally referred to as hunting spiders, but T. erebus built a small prey-capture web. T. erebus also preyed on segestriid spiders, then used their webs to catch more prey, this being an unusual example of a spider using, as a tool for predation, the spinning-work of another species from an unrelated family. T. erebus used specialised behaviours to prey on nesting cursorial spiders. Prey was either grasped or stabbed; the venom of T. erebus was highly potent against spiders. Experiments indicated that vision was of little or no importance in the predatory behaviour of T. erebus. The behaviour of T. erebus is compared to that of Portia, a web-building salticid spider which is very versatile in its predatory behaviour and has acute vision. T. erebus is discussed in relation to hypotheses concerning gnaphosid and salticid evolution.
Jumping spiders of the family Salticidae have well developed eyes, which mediate their highly stereotyped predatory and commnicative behaviour. Experimental studies presented here provide behavioural evidence that salticids are capable of perceiving televised (video) images. Juvenile and sexually mature individuals of the dimorphic jumping spider, Maevia inclemens (Walckenaer), were tested in V-maze choice test and behavioural chambers where they were allowed to view images of videotaped prey and spiders presented on Sony Watchman micro-television unuits. Results from this study suggest that jumping spiders interpret video images as real, because: (1) spiders did not discriminate between live prey and its simulateously presented video image; and (2) they behave appropriately when presented with televised images of prey insects (e.g. stalk and attack televised prey), conspecifics (e.g. courtship and sexual receptivity behaviour directed toward televised conspecifics) and heterospecific jumping spider species (e.g. retreat from predator stimulus). These observations support a previous estimate, of low critical flicker fusion frequency values in this group, and enable the development of a powerful new method for the study of animal behaviour.
Prey‐preference behaviour of three species of araneophagic salticid (P. labiata from the Philippines and Sri Lanka, P. africana from Kenya and Uganda, and P. schultzi from Kenya) is studied in the laboratory for the first time. “Well‐fed” (7 day fast) and “starved” (14 day fast) males and females of each species have a pronounced preference for web‐building spiders over insects, and a less pronounced preference for salticid spiders over insects. Also, well‐fed and starved males and females of these species prefer web‐building spiders to salticids. Preferences for taxonomic type of prey are the same regardless of whether living, active prey or dead, motionless lures are used, suggesting that all these araneophagic salticids can distinguish between the different taxonomic categories of prey without reference to their different movement patterns. For each species, females—relative to males—preferred larger prey. When extra‐starved (21 day fast), males and females of all species appeared to take prey of different taxonomic categories indiscriminately. Findings from this study are discussed in relation to earlier studies on myrmecophagic salticids and on other araneophagic salticids.
Previous work has shown that the mosaics of Layer I receptive segments in the tiered principal (AM) retinae of most jumping spiders (Salticidae) are organised as regular arrays of light guides which are competent to sustain fine visual discriminations. The re-tinae are narrow strips which arise in development by lateral compression of a primordial hemispherical mono-layer of nascent receptive segments. Foveal Layer I re-ceptive segments each contain a single rhabdomere in most species, but simple geometry suggests that the de-velopmental route will generate a vertical 'suture line' of sampling ambiguity in which contiguous rhabdomeres of adjacent segments act as single light guides. In members of two primitive subfamilies, the Lyssomaninae and Spartaeinae, such suture lines are indeed present; their optical consequences are discussed in the context of the evolution of foveal rhabdomeres that are long light guides. In several notionally advanced subfamilies collectively termed the Salticinae here for convenience, suture lines have been eliminated by rotations of the positions of single rhabdomeres with respect to the longi-tudinal axes of their receptive segments. The resulting mosaic patterns of rhabdomere distribution are similar in genera distantly related within the Salticinae, and are not bilaterally symmetrical with respect to horizontal axes bisecting the boomerang-shaped receptor fields. The basic pattern is not disturbed in genera in which Layer I receptive segments are separated from neigh-bours by a structureless extracellular matrix. This sepa-ration of segments conserves the organisation found in juvenile jumping spiders designated as 2nd instar by Blest (1988). The present material confirms that the evo-lution of retinal tiering preceded that of a foveal Layer I mosaic of high acuity in the Lyssomaninae as well as Spartaeinae (Blest and Carter 1987). The evolutionary history of Layer I in the Salticinae remains obscure.
aim . . . is to argue for a developmental approach to the study of instinctive behavior—behavior that is species-typical and that has some adaptive function
research on early parent-offspring vocal-auditory interactions in ducks
discuss the implications of epigenetic and ecological thinking for understanding certain key relationships between development and evolution
imprinting / critical periods / development of alarm call responsibility in mallard duckings / acoustic features of alarm calls (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Mimetus sp. indet. and Mimetus maculosus, from New Zealand and Australia, respectively, were studied in the laboratory and in nature. Behaviourally, the two species were very similar. Each was found to be primarily an araneophagic spider which invaded alien webs, acted as an aggressive mimic by performing a variety of vibratory behaviours to which the prey-spider responded as it normally would to its own prey, and attacked by lunging at close range, subduing its victim with a strong, apparently spider-specific venom while holding the spider in a ‘basket’ formed by its spine-covered legs. In nature, these mimetids were observed to feed on a restricted range of spiders: orb web-building araneids and space web-building theridiids. Sometimes, they occupied other types of webs, but in the laboratory they captured only araneids and theridiids efficiently. They captured non-cribellate amaurobiids considerably less efficiently, and never captured other types of spiders. Occasionally, the mimetids fed on insects ensnared in araneid and theridiid webs and on eggs of theridiids. Experimental evidence indicated that vision was of little or no importance in the predatory behaviour of these mimetids. The behaviour of the mimetids is compared to that of Portia, an araneophagic web-invading salticid, and the results of this study are discussed in relation to hypotheses concerning salticid evolution.
Portia fimbriata from Queensland, a previously studied jumping spider (Salticidae), routinely includes web-building spiders and cursorial salticids in its diet, both of these types of prey being dangerous and unusual prey for a salticid. The present paper is the first detailed study ofP. fimbriata's prey preferences. Three basic types of tests of prey preference were used, providing evidence that (1)P. fimbriata males and females prefer spiders (both web-building spiders in webs and salticids away from webs) to insects; (2)P. fimbriata males and females prefer salticids to web-building spiders; (3)P. fimbriata males and females prefer larger spiders to smaller spiders; (4) there are intersexual differences in the preferences ofP. fimbriata for prey size, females preferring larger prey and males preferring smaller prey; and (5)P. fimbriata's prey preferences are not affected by a prior period without food of 2 weeks. When preferences were tested for by using both living, active prey and dead, motionless lures, the same preferences were expressed, indicating thatP. fimbriata can distinguish among different types of prey independent of the different movement patterns of different prey.
In a laboratory study, 12 different experimental set-ups were used to examine the ability ofPortia fimbriataa web-invading araneophagic jumping spider from Queensland, Australia, to choose between two detour paths, only one of which led to a lure (a dead, dried spider). Regardless of set-up, the spider could see the lure when on the starting platform of the apparatus, but not after leaving the starting platform. The spider consistently chose the ‘correct route’ (the route that led to the lure) more often than the ‘wrong route’ (the route that did not lead to the lure). In these tests, the spider was able to make detours that required walking about 180° away from the lure and walking past where the incorrect route began. There was also a pronounced relationship between time of day when tests were carried out and the spider's tendency to choose a route. Furthermore, those spiders that chose the wrong route abandoned the detour more frequently than those that chose the correct route, despite both groups being unable to see the lure when the decision was made to abandon the detour.
The foraging behaviours of Argyrodes antipodiana (O.P. Cambridge) were observed in the laboratory and in nature. A. antipodiana is a kleptoparasitic spider primarily dependent on one host, an orb web-building spider, Araneus pustulosa. To exploit the host, A. antipodiana builds a support web on which it relies heavily. The support web is attached to the host’s web and enables A. antipodiana, without being detected, to swing to safety with stolen food bundles, remove gleaned insects, and feed with the host.Although the host provides food for A. Antipodiana, it is also a potential predator which the kleptoparasite must avoid. Here the support web is again invaluable as it is a structure into which A. antipodiana can swing if threatened by the host.Besides being kleptoparasitic, A. antipodiana is also araneophagic (i.e., it eats spiders). A. antipodiana preys on the host when it is vulnerable during moulting and also captures the host’s spiderlings by using aggressive mimicry.A. bantipodiana may also obtain food without using the host. It builds a sticky space web, unattached to a host’s web, with which it can catch flies, albeit inefficiently.The foraging behaviours of A. antipodiana are compared with those of other studied species of Argyrodes, and speculations concerning phylogenetic relationships between behavioural groups within the genus Argyrodes are presented.
The eyes of spiders are ocelli, and it is natural to compare their performance with that of compound eyes and of the ocelli of insects. The latter, which are underfocused and usually possess receptor mosaics of indifferent quality (Wilson 1978), are better known than those of arachnids, and have not encouraged workers to examine those of spiders in much detail. Nevertheless, the ocelli of spiders range from the principal eyes of jumping spiders whose sophisticated organisation sustains high visual acuities (Land 1969a; Eakin and Brandenburger 1971; Jackson and Blest 1982a; Blest and Price 1984) to many, perhaps the majority, that can hardly be supposed to sustain much in the way of image analysis at all.
Recent foraging models split the problems animals face into two stages: (1) the updating of information about alternative food sources and (2) the determination of behavior subject to this information (reviewed by Kacelnik and Krebs, 1985;Kacelnik et al., 1987;Stephens and Krebs, 1986). The cognitive abilities of different foragers are crucial at both stages. Species with limited cognitive abilities may rely heavily on relatively restrictive and inflexible decision rules. On the other hand, species with superior abilities to acquire information about the distribution, availability, and relative profitability of different food types may show superior and more flexible performance in foraging tasks (Pyke et al., 1977;Orians, 1981;Kamil and Mauldin, 1987;Schoener, 1987). In spite of the crucial importance of cognition for foraging performance, foraging studies, with few exceptions, rarely include information about the actual cognitive abilities of the animals under investigation. Nevertheless, all studies of foraging behavior make explicit or implicit assumptions about what animals perceive and know.
An African gray parrot (Psittacus erithacus), Alex, trained to label vocally collections of 1-6 simultaneously presented homogeneous objects, correctly identified, without further training, quantities of targeted subsets in heterogeneous collections. For each test trial Alex was shown different collections of 4 groups of items that varied in 2 colors and 2 object categories (e.g., blue and red keys and trucks) and was asked to label the number of items uniquely defined by the conjunction of 1 color and 1 object category (e.g., ''How many blue key?''). The collections were designed to provide maximal confounds (or distractions) and thus replicate the work of Trick and Pylyshyn (1989) on humans. Humans count rather than subitize under such conditions. Alex's results (83.3% overall accuracy) are therefore discussed in terms of their relation to human numerical competence, particularly with respect to counting.
This chapter discusses the data collected during more than a decade of research, that provide direct comparisons between mammalian cognitive abilities and those of an African Grey parrot. The study of complex cognitive abilities in animals is often built upon two premises. First, there is usually some evidence upon which to base the hypothesis that the subjects of the study might indeed possess the abilities that are to be tested; second, the experimenter is assumed to have a viable paradigm with which the testing can be performed. Grey parrots had been shown to be capable of learning the kinds of symbolic tasks that most researchers agree are important prerequisites or co-requisites for complex cognitive and communicative skills. These findings suggest that a Grey would be a good choice for studies of more complex abilities-tasks that might, for example, involve capacities for categorization, relational concepts, and quantification.
Portia is a salticid that preys on other spdiers and Euryattus sp. is a salticid that nests inside suspended rolled-up leaves. Portia and Euryattus are sympatric at a site near Cairns but not known to be sympatric at other sites studied. Portia from the Cairns site practices a unique prey-specific predatory behaviour against Euryattus, and Euryattus from this site is efficient at detecting and defending itself against Portia. Euryattus, but not Portia, is present at a site near Davies Creek which, although only 15km from the Cairns site, is more xeric and at a higher elevation. Three types of tests were carried out to compare Portia's efficiency at catching adult allopatric versus sympatric Euryattus (Test 1), allopatric Euryattus juveniles versus juveniles of another salticid species on which Portia is known to prey (Test 2) and allopatric versus sympatric Euryattus juveniles (Test 3). Portia behaved similarly toward allopatric (Davies Creek) and sympatric (Cairns) Euryattus, except that it attacked and killed allopatric more often than sympatric Euryattus. Allopatric Euryattus, in contrast to Cairns Euryattus, appeared not to recognize an approaching Portia as a predator. -Authors
This study is concerned with two properties of cognitive mapping. The first is plasticity, by which I mean the ability of an animal to reorganize its previous experience of a given situation. Thus, for example, when modifications are introduced into a familiar spatial task, some animals can find original solutions; they do not become lost and they can still reach the goal. The second property is optimalization. It entails the choice and the planning of the best adapted solution: for example, taking the most direct of several possible ways to reach a goal.
Communication occurs when one individual, the sender, changes the behaviour of another individual, the receiver, indirectly by providing it with a special stimulus, the signal (see J.R. Krebs and Dawkins 1984; Jackson 1982a; W.J. Smith 1977). During intraspecific interactions, spiders employ a wide variety of signals which may be exchanged over chemical, visual, vibratory, tactile or auditory sensory channels. Chemical signals, or semiochemicals, appear to be the most primitive mode of communication in the arachnids and have probably been retained in some form in all spider families. We will not attempt to provide a comprehensive review of work which has been done on spider semiochemicals (see Tietjen and Rovner 1982), but instead we will emphasize more recent work on pheromones from our own laboratory. The term pheromone is used to describe olfactory and contact chemicals that are used during intraspecific interactions.
Publisher Summary This chapter provides a preliminary account of some of the selective costs and benefits that are involved in the evolution of learning by natural selection. The term “evolution” refers to a change in the population-typical phenotype over some period of time. The aim of a cost-benefit analysis is to allow making statements about the conditions under which particular kinds of adaptations are likely to evolve and explain the reasons for these adaptations being observed in some populations and not in others. Such statements may be either qualitative or quantitative and they may account to a greater or lesser degree for the details of an adaptive trait. The chapter emphasizes on qualitative considerations. It identifies six potential selective costs of learning––namely, delayed reproductive effort and/or success, increased juvenile vulnerability, increased parental investment in each offspring, greater complexity of the central nervous system, greater complexity of the genome, and developmental fallibility.
The evolution of female mating preferences is an important key to
understanding the evolution of signal diversity. Several hypotheses for
preference evolution invoke different processes but all can produce the
same end results: thus comparisons of extant traits and preferences
within and among populations have made little progress in discriminating
among competing hypotheses. Some of these hypotheses, however, do make
different predictions as to the historical sequence of trait-preference
evolution, and thus can be discriminated with appropriate phylogenetic
analyses. We explore this approach in an analysis of the evolution of
calls and call preferences in a monophyletic group of frogs, the
Physalaemus pustulosus species group. In this clade there are
pre-existing preferences for four call traits. These data reject
hypotheses that invoke coevolution (good genes, runaway sexual
selection) and females evolving preferences to choose males providing
better resources, and instead support the hypothesis of sensory
exploitation that suggests that males evolve traits that match
pre-existing biases in the female's sensory system. We suggest that some
of the difficulty in understanding preference evolution might derive
from defining a preference only by those extant stimuli that elicit the
preference. Our results suggest that preferences might be more general,
and that signal diversity might arise from alternative means for
eliciting the same preference. Furthermore, we discuss some difficulties
with utilizing both population-based comparisons and phylogenetic
approaches and suggest that the greatest progress will be made by
addressing the problem of preference evolution at several levels of
analysis.
The effects of goal visibility and distance on detour behaviour in 2-day-old chicks, Gallus gallus domesticus, were investigated. Cagemates were used as goals and placed behind barriers that concealed them to various degrees. Times needed to develop itineraries to pass round the barrier between the chick and the goal decreased with decreased visibility and increased distance of the goal. Under similar conditions of physical concealment of the goal, however, vertical-bar barriers took longer to negotiate than horizontal-bar barriers. Disocclusion of the goal mediated by the animal's movements did not seem entirely to account for this asymmetry: chicks seemed to have difficulty in considering vertical bars that concealed a goal as natural obstacles. Visual interaction between cagemates used as goals made the task easier, whereas the number of cagemates visible behind the barrier had no effect. The results suggest that most of the alleged difficulty of chicks in detour problems arises from the use of procedures that maximize confounding motivational factors and of unnatural stimuli that do not allow the animal to perceive the 'barred character' of an obstacle.
Portia is a genus of jumping spiders which invade alien webs and use aggressive mimicry to prey on the resident spiders. Portia’s aggressive mimicry repertoire includes numerous different vibratory displays. Portia’s aggressive mimicry displays are compared to its grooming and disturbance behaviours, and hypotheses are discussed concerning the evolution of specific aggressive mimicry displays from specific grooming and disturbance behaviours. The contexts in which Portia and a variety of other salticids and spiders from other families groom and perform disturbance behaviours are investigated. Special attention is given to the conflict theory of ritualisation which has been useful in studies of other animals. This theory is not found to be very useful, however, for understanding the evolution of Portia’s aggressive mimicry displays.
Conditional strategies and interpopulation variation in the mating and predatory behaviour of salticid spiders are reviewed. A functional approach is adopted, and defended, in which specified behavioural phenotypes are accounted for, in large part, by specified selection factors. Courtship versatility, in which a male's behaviour depends on the female's maturity and location, is common in the Salticidae. If a male encounters an adult female in the open, where there is ample ambient light, he performs vision-dependent displays (Type 1 courtship) in front of her. If he encounters an adult female inside her nest, he uses different displays (Type 2 courtship) which are not vision–dependent and consist of various tugging, probing and jerking movements on the silk of the nest. These displays apparently send vibratory stimuli to the female. When a male encounters a subadult female inside her nest, he initially performs Type 2 courtship, then spins a second chamber on the nest and cohabits until the female moults and matures. A modification of optimal foraging theory has been used to examine factors that influence interpopulation variation in male courtship persistence. A study of five populations corroborated predictions from the model. Persistence appears to be related to female availability. Female availability is related to local phenology, which is, in turn, related to local climate. Complex examples of predatory versatility also have evolved in the Salticidae, especially in the genus Portia. All species of Portia studied are araneophagic spiders that invade other spiders' webs and practise aggressive mimicry. Portia fimbriata, uniquely among Portia species studied, uses specialised behaviour to prey on other salticids. Portia fimbriata and one of the salticids on which it preys, Euryattus sp., appear to be co-adapted to each other.
The terms "reversed-route detours' and "forward-route detours' are introduced to distinguish between detours that require moving away from a goal and those that do not. The first evidence under controlled laboratory conditions is provided that salticids can perform reversed-route detours. Two species were tested: 1) Portia fimbriata, a web-invading salticid from Queensland, Australia, that normally preys on web-building spiders; 2) Trite planiceps, an insectivorous cursorial salticid from New Zealand. Although both of these species completed reversed-route detours, T. planiceps was much more dependent on prey movement than P. fimbriata. Interspecific differences appear to be related to the different predatory styles of these two salticids. -Authors
Portia fimbriata and Portia labiata are specialized web-invading species that eat other spiders. Euryattus sp., Euophrys parvula, Marpissa marina, Trite auricoma and Trite planiceps are more typical cursorial hunters of insects. Salticids will initiate detours toward motionless prey; they are more inclined to initiate detours toward moving than toward motionless prey, and tend to complete detours even when prey that had been moving at the start remains stationary during the detour. Prey movement makes the salticid more likely to stalk and attack when prey is only a few centimetres away and in a position from which it can be reached by a straightline pursuit. Portia is more inclined than the other salticids to initiate detours to motionless prey, then to stalk and attack motionless prey when close, than the other salticids are. -from Authors
Portia is a jumping spider that invades other spiders' webs, makes vibratory signals that deceive the resident spider (aggressive mimicry), then attacks and eats the spider. Portia exploits a wide range of prey-spider species. Evidence is provided from observation and experimentation that Portia uses a trial-and-error method as part of its strategy for deriving appropriate signals for different prey. To use this method, Portia first broadcasts an array of different signals, then narrows to particular signals as a consequence of feedback from the prey spider. Feedback can be web vibration or seeing spiders move, or both. This appears to be an example of deception involving at least a limited form of learning, an uncommon phenomenon in invertebrates.
The stalking behaviour of four species of jumping spiders,Portia fimbriata, P.labiata, P.schultziandP.africana, was examined to determine whetherPortiaopportunistically exploits situations in which the prey spider is distracted by environmental disturbances. Disturbances were created mainly by wind blowing on webs and a magnet shaking webs. All fourPortiaspecies moved significantly further during disturbance than during non-disturbance, a behaviour labelled ‘opportunistic smokescreen behaviour’.Portiacan discriminate between spiders and other prey such as live insects, wrapped-up insects in the web, and egg sacs, becausePortiaused opportunistic smokescreen behaviour only against spiders and not against these other types of prey. If the location of disturbances and the location of prey differ,Portiacan accurately discriminate between them.Portia’s smokescreen behaviour apparently is a true predatory tactic becausePortiaattacked prey more often during disturbances than at other times. Smokescreen behaviour appears to work in part because the disturbances thatPortiauses for smokescreens interfere with the prey's ability to sensePortia’s stalking movements.
Chicks,Gallus gallus domesticus, of 2 and 6 days of age were presented with a goal-object that was made to disappear behind one of two screens opposite each other. Chicks proved able to choose the correct screen when the goal-object was a social partner (i.e. a red ball on which they had been imprinted), whereas they searched at random behind either screen when the goal-object was a palatable prey (i.e. a mealworm). Chicks, however, appeared able to make use of the directional cue provided by the movement of the mealworm when tested in the presence of a cagemate. These results suggest that previous failure to obtain detour behaviour in the double screen test in the chick was not due to a cognitive limitation, but rather to the evocation of fear responses to the novel environment that interfered with the correct execution of the spatial task.
Two-day-old chicks, Gallus gallus domesticus, were tested in a detour situation requiring them to abandon a clear view of a desired goal (a small red object on which they had been imprinted) in order to achieve that goal. The chicks were placed in a closed corridor, at one end of which was a barrier with a small window through which the goal was visible. Two symmetrical apertures placed midline to the corridor allowed the chicks to adopt routes passing around the barrier. After entering the apertures, chicks showed searching behaviour for the goal and appeared able to localize it, turning either right or left depending on their previous direction of turn. Thus, in the absence of any local orienting cues emanating from the goal, chicks were aware of the existence of an object that was no longer visible and could represent its spatial localization in egocentric coordinates.
The modern arachnids are the only group of arthropods in which the main organs of sight are camera-type eyes, not unlike our own, rather than compound eyes. The copepod crustaceans also lack compound eyes, but their nauplius eyes are rarely more than a trio of simple eye-cups, with a handful of receptors each. By contrast, spider eyes at their best have retinae with 103 to 104 receptors, and in the salticid Portia the inter-receptor angles may be as small as 2.4 min of arc (Williams and McIntyre 1980), which is only six times greater than in man (cone spacing 0.42 min), and is six times smaller than in the most acute insect eye (the dragonfly Aeschna, minimum inter-ommatidial angle 14.4 min; Sherk 1978). Thus, in some spiders, but by no means all, vision is excellent, and rivalled amongst invertebrates only by the cephalopod molluscs.
In der vorliegenden Arbeit wurde versucht, Richtlinien fr die Untersuchung von Spinnenaugen aufzustellen. Die Untersuchung erstreckt sich auf die Anatomie und die Optik der Augen und auf die Reaktionen der lebenden Tiere. Durch Bercksichtigung dieser drei Faktoren gelingt es, zu einem vollstndigen Bild des Sehvermgens von Spinnen zu gelangen.I. Der allgemeine Teil der Arbeit befat sich mit den Methoden der Untersuchung von Optik und Anatomie.1.
Die optischen Konstanten der Augen sind nur teilweise einer genaueren Messung zugnglich. Zu messen sind, ohne da bedeutende Fehlerquellen zu bercksichtigen sind, die vordere Brennweite, der Krmmungsradius und der Abstand des Knotenpunktes von dem hinteren Brennpunkt. Aus diesen Werten lt sich ein reduziertes Auge berechnen. Vor allem ist auf die Lage des Knotenpunktes in den Augen hingewiesen. Von seiner Lage hngt das Gesichtsfeld des Auges und der Winkelabstand der Rhabdome ab. Unmglich ist eine genaue unmittelbare Messung der hinteren Brennweite, die bis heute immer versucht wurde, die aber infolge der geringen Kenntnisse der Brechungsindizes und der hinteren Krmmung der Linse nur zu angenherten Werten fhrt.
2.
Mit dem Mikroaugenspiegel gelang es, einen Schritt weiter zu kommen und den Augenhintergrund im aufrechten, vergrerten Bilde zu sehen.
3.
Fr die Messung der Gesichtsfelder werden neue Methoden angegeben. a) Das Abtasten des Augenleuchtens mit einem kardanisch aufgehngten Mikroskoptisch und der daraus folgenden graphischen Darstellung. b) Die Berechnung aus der Anatomie unter Bercksichtigung der Lage des Knotenpunktes. c) Die Prparation des ganzen Auges in Kanadabalsam.
4.
Der Winkelabstand der Rhabdome, der ausschlaggebend fr die Perzeption der Form durch das Auge ist, wird aus dem absoluten Abstand und der Lage des Knotenpunktes berechnet. In einigen Fllen gelingt es, den Winkelabstand der Rhabdome am lebenden Tier mit Hilfe des Mikroaugenspiegels festzustellen.
5.
Das gesamte Gesichtsfeld einer Spinne hngt von der Richtung der Augenachsen und der Gre der Einzelgesichtsfelder ab, nicht von der Gre der Augen und ihrer Anordnung am Kephalothorax. 6. Eine Akkommodationsvorrichtung ist fr diese Augen mit kleiner Brennweite und groben Retinaraster nicht ntig.
7.
Es besteht ein Zusammenhang zwischen der Pigmentverkleidung der Rhabdome und dem ffnungsverhltnis der Linse.
II. In dem besonderen Teile der Arbeit werden diese Richtlinien auf den Gesichtssinn der Salticiden angewendet.1.
Die Anatomie der Augen wird in Hinsicht auf ihre Leistungsfhigkeit untersucht. Der eigenartige Bau der Retina der HA wird aufgeklrt.
2.
Die Augen werden als reduzierte Systeme berechnet.
3.
Mit dem Mikroaugenspiegel gelingt es, die Bewegung der Retina im HA zu erkennen. In den HSA und den VSA werden die Rhabdome im aufrechten Bilde gesehen.
4.
Es wird eine Erklrutig des farbigen Kornealreflexes versucht.
5.
Die Gesichtsfelder der VSA und HSA ergnzen sich. Die VSA haben einen binokularen Sehraum von etwa 40. Die sehr kleinen. Gesichtsfelder der HA liegen innerhalb des binokularen Sehraumes der VSA.
6.
Der Winkelabstand der Rhabdome ist in den einzelnen Augen verschieden. Den grten haben die HSA mit 2. Die HA und VSA haben eine Stelle der engsten Rhabdome. Der Abstand der Rhabdome der VSA ist in der Mitte 35, an der Peripherie 2. Der Abstand der Rhabdome der HA ist in der Mitte 12, an der Peripherie 40.
7.
Die HMA befinden sich in Rckbildung.
8.
Die Salticiden haben einen Reaktionswinkel von 1. Sie laufen bis auf 4-3 cm an die Beute heran, schleichen bis auf 1,5-1 cm und berfallen dann im Sprung. Die fhren 6-5 cm, im uersten Falle 8 cm von den entfernt Balztnze auf.
9.
Teilweise geblendete Spinnen zeigen Abweichungen von diesem Verhalten. Spinnen mit geblendeten HA heben die Vorderbeine, klettern ungeschickt und laufen bis auf Sprungweite an die Beute heran, ohne zu schleichen. Spinnen mit geblendeten VSA beginnen auf weitere Entfernung zu schleichen, ihre Sprnge auf die Beute sind weiter. Ein geblendetes HA bedingt das Heben des Beines der entsprechenden Seite, ein geblendetes VSA hat die gleichen Erscheinungen zur Folge wie das Blenden beider VSA.
a)
Die HSA (oder VSA) nehmen den ersten Reiz auf.
b)
Die Reizung eines Rhabdomes gengt, um das Tier auf eine Beute hinzulenken.
c)
Die VSA fhren die Beute den HA zu.
d)
Mit den HA kann die Spinne auf relativ groe Entfernung Formen perzipieren.; die HA sind Augen fr ein Sehen in die Ferne.
e)
Die Muskeln der HA sind keine Akkommodationsmuskeln. Sie vergrern die Gesichtsfelder der HA, indem sie die Retina zur Seite ziehen und ermglichen vielleicht ein Sehen mit bewegtem Auge.
f)
Die VSA sind angepat an ein Sehen in der Nhe; sie ermglichen in ihrem Sehbereich eine Entfernungsperzeption.
The anterior median (AM) or principal eyes of the primitive jumping spider, Portia fimbriata (Doleschall), are miniature telephoto systems (Williams & McIntyre, 1980). Another study on the AM eyes of Plexippus suggests that most salticid principal eyes may be of similar design (Blest, Hardie, McIntyre and Williams, 1982). Both studies assumed, from anecdotal evidence (e.g. Forster, 1979), that jumping spiders can make visual discriminations between prey and mates at distances of ca. 20 cm. This estimate is necessary to the functional analyses that were essayed; because it is impossible to make sufficiently accurate direct measurements of some of the parameters of these small eyes, their optics can only be modelled with confidence when something is known about what they are designed to see. Land (1969 a, b), in an elegant optical study, followed Drees (1952) in stating that jumping spiders respond to significant objects some 5-10 body-lengths in front of them. In the case of Portia, this would be a distance of no more than 10 cm at most. Recognition of objects is mediated through the AM eyes (Drees, 1952).
The prey-catching behavior of jumping spiders (
Attidae) is linked to the possession of a highly organized and functionally specialized visual system. Hunting behavior is divided into a number of units (tasks), each of which is relegated by a particular pair of eyes or portion thereof. These tasks are behaviorally and physiologically coordinated. Jumping spiders can adjust their hunting behavior and the order in which the various units are performed as the occasion demands. Such reactions necessitate the immediate perception of appropriate information, which means that they respond to stimuli as they occur rather than depending on some predetermined chain of responses. (36 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Anti-predator defence behaviour of Argiope appensa (Fuesslin) (Araneae, Araneidae) was studied in the laboratory. The most frequent response of adults and large juveniles of A. appensa to disturbance was pumping, a behaviour during which this web-building spider moved its body rapidly up and down with its legs remaining on the silk. When disturbed, small juveniles differed from adult females and larger juveniles by often dropping from the web instead of pumping. Argiope appensa sometimes put its web betweeen itself and stimuli from potential predators by shuttling from one side of the hub to the other. Argiope appensa occasionally tugged on the web but this behaviour appeared to be primarily a component of prey-catching sequences instead of defence. Experiments were carried out to determine the types of stimuli that elicited pumping. Lightly touching the spider or its web, forcefully hitting the web, and air movement elicited pumping but there was no evidence that chemical stimuli from potential predators were important.
1.
Given the right circumstances, toads will detour round a paling fence to reach their prey on the other side. In programming this manoeuvre, toads take into account both the position of the fence and the distance of the prey (Fig. 1). Should there be a gap in the fence, which offers a more direct approach, toads will aim for that instead (Fig. 2).
2.
The argument developed in this paper is that, when a toad decides upon a particular approach, it is guided by the sum of its reactions to several individual features of the situation, such as the length of the fence, the presence or absence of gaps, the gaps' width (Fig. 7) and their proximity to the prey (Fig. 11) and to the toad's long axis (Fig. 10). When there are several possible approaches, toads will select the gap (or edge) which has the most attractive combination of features.
3.
The relative attraction of gaps can be manipulated and toads will then shift their preference. Normally, toads head for the gap lying closest to the prey and to their long axis (Figs. 9a and 12b). However, if the relative salience of a more peripheral gap is increased the bias towards the closer gap is reduced (Fig. 9b).
4.
Toads tend to choose the closest gap even when it is inappropriate to do so. They seem unable to use the spatial information potentially available to them to pick out the shortest, unobstructed path to their prey. The major support for this view comes from the way they treat double fences composed of two rows of palings. With both fences unbroken, toads usually detour around them (Fig. 2d). However, when a gap is inserted in the front fence, they will often aim for that, regardless that the rear fence blocks their subsequent approach (Figs. 2c and 4). If palings are added to join the ends of the two fences, toads continue to aim for the gap, though once they have entered the space between the two fences, all they can do is to retrace their steps.
5.
It is not that toads are blind to the rear fence. They can detect gaps in it (Fig. 8a) and their behaviour is influenced by the distance between the rear fence and their prey (Fig. 6). Nonetheless, a gap restricted to the front fence is still treated as a gap, but as less attractive than one extending through both fences (Fig. 8b). And, if such a gap is close to the toad's midline and the prey, then toads are drawn to it, rather than to the ends of the fence.
Adults and large juveniles of Queensland Portia fimbriata, a salticid spider known to prey on other spiders (including other salticids), are shown to use prey-specific predatory behaviour against Euryattus sp., one of the salticids on which it feeds. Euryattus females are unusual because they nest inside suspended rolled-up leaves. P. fimbriata used vibratory displays to lure Euryattus females from their nests. These displays seem to mimic the courtship displays of Euryattus males. Other species of Portia and other populations of P. fimbriata, in habitats in which Euryattus is not known to occur, did not practise this prey-specific behaviour. In the laboratory, Euryattus — but not Jacksonoides queenslandica, another salticid on which P. fimbriata is known to feed — readily recognized approaching Portia as a potential predator. A possible evolutionary arms race between Portia and Euryattus is discussed.
The sensory exploitation hypothesis explains male secondary sexual characters as adaptations to exploit female responses that evolved in non-sexual contexts. The water mite Neumania papillator takes up a characteristic posture, the net-stance, in order to detect vibrations produced by copepod prey. Courting males vibrate their legs (‘male courtship trembling’) near females, and previous research shows that females respond to the vibrations as if they were produced by prey. The sensory exploitation hypothesis for male courtship trembling was tested by constructing a cladogram of N. papillator plus nine confamilial ingroup species and three outgroup species using 28 morphological and behavioural characters. Courtship and predatory behaviour were mapped onto the resultant tree. Net-stance evolved once and male trembling either evolved concomitantly with net-stance or twice thereafter. When taken together with previous behavioural evidence, this cladistic study strongly supports sensory exploitation as an explanation for male courtship trembling in unionicolid mites.
Spiders are well known predators of insects, but some even eat their own kind. For most species, eating other spiders appears to be a largely opportunistic occurrence, a larger or faster individual overpowering another in achance encounter. There are at least a few spider species, however, for which araneophagy (predation on other spiders) is routine (e.g.Jackson & Poulsen 1990). Some of these species employ strategies based on deceit of their spider prey. In this article, I use images of deception, mimicry and trickery to convey the functional significance of a predators behaviour and not to imply cognition. Use of deceit by araneophagic spiders may be especially important because another psider is a potential predator as well as potential prey.
Jumping spiders turn to face moving objects. These turns are mediated by the lateral eyes. They can be accomplished accurately whether or not the spider sees the relative movement of the stimulus across the retinae which would normally result from such a turn. The spider’s response to an adequate stimulus may be: (i) to make a ‘complete’ turn resulting in fixation by the antero-median eyes; (ii) to make a ‘partial’ turn of 10–20°, whose magnitude is independent of stimulus position, and which does not result in fixation, or (iii) to ignore it. To be seen, a stimulus must subtend more than 0–7° (slightly less than the distance between receptors) and must move through a minimum angle of about i°. The probability of a turn being made is greatest for stimuli 40–90° from the spider’s front, and decreases to a low value for stimuli behind the animal, and immediately in front of it. Repeated presentation of a stimulus to one part of the retina results in a rapid decrease to zero of the probability of a turn being made, but turns can still be evoked by moving the stimulus a few degrees to a previously unstimulated part of the retina. Habituation does not affect the sizes of the few turns that are made. Dishabituation can be caused by mechanical stimulation, or it may occur spontaneously. The fields of view of the lateral eyes have been measured in the horizontal plane by blinding each eye and determining the parts of the visual field from which turns could not be evoked. Three kinds of response mediated by the lateral eyes, in addition to turns towards the stimulus, are described.