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Early stages of orb web construction in Araneus diadematus Clerck
Abstract and Figures
The early stages of orb web construction are the least studied and the most poorly understood, because the behaviour of the spider at that stage lacks the repetitiveness of later stages, the timing is unpredictable and the moves of the spider cannot be deduced from the finished web.
In the present study, all moves of the spider during web construction were recorded using computerised image analysis. The early stages of web construction of several webs were then reconstructed from these recordings and analysed in detail.
The construction leading to the proto-hub was found to be highly variable. It was also found that during its construction, the spider employs a series of fixed behavioural patterns in seemingly random order. These patterns are 'designed' in a way to make it very likely that a proto-hub will emerge. Once the spider had established this proto-hub, its behaviour became more stereotyped and predictable.
The costs to explore a new site were estimated by measuring the distance walked by the spider. These costs were compared to the costs of adapting the framework of an existing web and it was found that rebuilding an existing web costs much less compared to building a web from scratch.
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... On the other hand, however, we still know very little about the process of habitat exploration and site selection that precedes web construction [96,97]. Orb-web spiders engage in extensive site exploration [98], and generally match the shape of their webs to both the available space [99] and the available silk supplies [100]. Most web-building spiders are not picky when it comes to attaching their webs to their surroundings and will choose any suitable structure-usually a rigid or semi-rigid structure in order to avoid web damage from wind movements [5,101,102]-although some spiders also attach their webs to moving structures, such as leaves and grass, without it negatively affecting their web-building efficiency or resultant webs [103]. ...
... On the other hand, while some spiders are known to be able to find their burrows over long distances, likely using compass and path integration [119,120], no information, at least not to our knowledge, is available on the extent to which spiders rely on random-search patterns to find suitable web-building sites over longer distances. However, the hypothesis that many spiders engage in random searching and potential trial-and-error web-building behaviour on chosen sites is strengthened by the observations that some orb-web spiders, despite extensive site exploration prior to web-building [97], build a smaller explorative web when building at a new location [98], and readily move their webs when encountering low prey capture, or when suffering web damage [70,121,122]. ...
Spiders are ubiquitous generalist predators playing an important role in regulating insect populations in many ecosystems. Traditionally they have not been thought to have strong influences on, or interactions with plants. However, this is slowly changing as several species of cursorial spiders have been reported engaging in either herbivory or inhabiting only one, or a handful of related plant species. In this review paper, we focus on web-building spiders on which very little information is available. We only find well-documented evidence from studies of host plant specificity in orb spiders in the genus Eustala, which are associated with specific species of swollen thorn acacias. We review what little is known of this group in the context of spider–plant interactions generally, and focus on how these interactions are established and maintained while providing suggestions on how spiders may locate and identify specific species of plants. Finally, we suggest ideas for future fruitful research aimed at understanding how web-building spiders find and utilise specific plant hosts.
... Despite the common occurrence of this environmental disturbance, the effects of moving anchors on orb web building behaviour and orb web design stand unexamined. The potential effects of moving anchors are particularly interesting because spiders carefully manage silk tensions in their webs during construction (Eberhard 1981;Mortimer 2019;Watanabe 2000;Wirth and Barth 1992;Zschokke 1996) and independent anchor movements should cause continuous tensions changes in any established threads. Studying the effects of moving anchors may additionally demonstrate whether spiders dedicate more time consolidating structural components of webs in mechanically taxing (non-windy) environments, and if the strong association between wind and anchor movement in nature causes spiders to change their webs as they do in windy conditions. ...
... Surprisingly, we found no significant effects of the shearing on both web building and a range of selected web features shown to be affected by blowing wind (Figs. 3, 4 and 5). This was unexpected because it is generally accepted that during web construction spiders regulate tensions (Eberhard 1981;Mortimer 2019;Watanabe 2000;Wirth and Barth 1992;Zschokke 1996) and our frame movements clearly affected the tensions in a cyclical fashion. Moreover, due to the common cooccurrence moving anchors and windy conditions in nature, one may have expected our artificial anchor movements to affect wind-sensitive web features, especially since our artificial anchor movements were slower than those observed in nature (Online Resource 1). ...
Many laboratory experiments demonstrate how orb-web spiders change the architecture of their webs in response to prey, surroundings and wind loading. The overall shape of the web and a range of other web parameters are determined by frame and anchor threads. In the wild, unlike the lab, the anchor threads are attached to branches and leaves that are not stationary but move, which affects the thread tension field. Here we experimentally test the effect of a moving support structure on the construction behaviour and web-parameters of the garden cross spider Araneus diadematus. We found no significant differences in building behaviour between rigid and moving anchors in total time spent and total distance covered nor in the percentage of the total time spent and distance covered to build the three major web components: radials, auxiliary and capture spirals. Moreover, measured key parameters of web-geometry were equally unaffected. These results call for re-evaluation of common understanding of spider webs as thread tensions are often considered to be a major factor guiding the spider during construction and web-operation.
... For vanishing displacement field, expressions (36) and (37) reduce to the membrane pre-stress state acting on the referential configuration B K : ...
... In order to introduce suitable a priori assumptions on the initial pre-stress, it is convenient to briefly recall the main steps of the process followed by spiders in creating their webs. The early stage of orb web construction, when anchor, frame and initial radii are laid, does not follow a fixed behavioral pattern [36]. Rather, the spider reacts in a flexible manner to adapt to a highly variable environment until the scaffold threads, made of major ampullate silk, stay in place. ...
In this paper we propose a continuum membrane model for the infinitesimal deformation of a spider orb-web. The model is derived in the context of axially-symmetric webs formed by radial threads connected with circumferential threads belonging to concentric circles. The continuous model inherits a specific fibrous structure from the original discrete web. In particular, a singularity arises at the centre of the membrane as a consequence of the intensification of the density of radial threads towards the centre of the web. Under suitable assumption on the tensile pre-stress acting in the referential configuration, the out-of-plane free transverse vibrations of a circular orb-web supported at the boundary are studied in detail. The accuracy of the model in describing a discrete spider web is numerically investigated.
... For vanishing displacement field, expressions (36) and (37) reduce to the membrane pre-stress state acting on the referential configuration B K : ...
... In order to introduce suitable a priori assumptions on the initial pre-stress, it is convenient to briefly recall the main steps of the process followed by spiders in creating their webs. The early stage of orb web construction, when anchor, frame and initial radii are laid, does not follow a fixed behavioral pattern [36]. Rather, the spider reacts in a flexible manner to adapt to a highly variable environment until the scaffold threads, made of major ampullate silk, stay in place. ...
... Descriptive and experimental work has been performed to understand web-building rules (Eberhard 1972(Eberhard , 1990Zschokke and Vollrath 1995;Zschokke 1996Zschokke , 2000Zschokke , 2011. This research suggests that spiders use many distinct external cues while building the web, such as prey-induced vibratory stimuli and prey nutrients (Pasquet et al. 1994;Blamires et al. 2011), wind intensity (Wu et al. 2013), gravity (Witt et al. 1976;Eberhard 1987;Vollrath 1988a, b), and humidity (Baba et al. 2014). ...
... The absence of frame threads, of radial organisation, and of the whole phase of temporary spiral building turned the cob and sheet web algorithms much more dependent on the initial, exploratory phase of web building (Benjamin and Zschokke 2004), a phase that is much more variable, mainly involving the fixation of threads over the substrate (Hesselberg 2015). The dependence of the exploration phase (and independence of the remaining phases) on the substrate has been experimentally demonstrated for the ancestral orb weavers: while the length of the exploratory phase increases with the complexity of the substrate, the length of the remaining phases does not match substrate complexity (Zschokke 1996). Since these remaining phases are either absent or much less organised in derived cob or sheet weavers, the net result is a web much more dependent on the exploratory phase, and thus much more connected to the substrate. ...
There is a tension between the conception of cognition as a central nervous system (CNS) process and a view of cognition as extending towards the body or the contiguous environment. The centralised conception requires large or complex nervous systems to cope with complex environments. Conversely, the extended conception involves the outsourcing of information processing to the body or environment, thus making fewer demands on the processing power of the CNS. The evolution of extended cognition should be particularly favoured among small, generalist predators such as spiders, and here, we review the literature to evaluate the fit of empirical data with these contrasting models of cognition. Spiders do not seem to be cognitively limited, displaying a large diversity of learning processes, from habituation to contextual learning, including a sense of numerosity. To tease apart the central from the extended cognition, we apply the mutual manipulability criterion, testing the existence of reciprocal causal links between the putative elements of the system. We conclude that the web threads and configurations are integral parts of the cognitive systems. The extension of cognition to the web helps to explain some puzzling features of spider behaviour and seems to promote evolvability within the group, enhancing innovation through cognitive connectivity to variable habitat features. Graded changes in relative brain size could also be explained by outsourcing information processing to environmental features. More generally, niche-constructed structures emerge as prime candidates for extending animal cognition, generating the selective pressures that help to shape the evolving cognitive system.
... The strong correlation of spiders with altitude is most likely due to the covariation between altitude and peatland character, since in the range of 758-944 m above sea level no other plausible reason for an influence of altitude on the spider community could be ascertained. Vegetation parameters such as height of the herb layer and herb cover also influenced the spiders' community composition, probably due to spiders' relationship to habitat structural diversity for, i.e., web attachment or concealment (Rypstra and Carter 1995;Zschokke 1996). ...
Peatlands host a large number of highly specialised species and are important carbon storage and freshwater reservoirs, but are heavily threatened by, e.g., peat extraction and drainage. For improved protection of peat-lands, the development of an ecological assessment system is necessary. Existing systems based, for instance, on peat formation and water level are rather coarse and differ between countries. The aim of the present study was therefore to evaluate the predictive power of biodiversity indicators-particularly invertebrates (Oribatida, Araneae, Carabidae) and vegetation-for more finely reflecting environmental conditions in Sphagnum-dominated peatlands in order to determine which taxonomic groups should be included in an ecological assessment system for peatlands. Therefore, we selected three plots in each of four peatland study sites in a German low mountain range and sampled the taxonomic groups using standard methods appropriate to represent assemblage structure and site diversity (Oribatida: Sphagnum samples; Araneae, Carabidae: pitfalls traps; vegetation: vegetation surveys). Our results indicate the necessity of implementing different taxonomic groups into an overall ecological assessment system, as all of them reacted differently to different ecological gradients. Oribatid mites were the best predictors of moisture, one of the most important factors in peatlands. Ground-dwelling spiders responded to several different factors; most remarkably, they strongly correlated with landscape area covered by peatland-related Natura 2000 habitat types, as a proxy for habitat quality. Carabidae most strongly correlated with the size of the Sphagnum plots, moss cover and moisture, but their species richness was very low. Vegetation, as the best established indicator group in peatlands, showed the weakest correlations to the tested environmental parameters, probably due to short-term changes in environmental conditions and a delayed response of the plant community. Hence, the set of most relevant environmental parameters can only be represented when multiple taxa are included in an assessment system. Also, overall biodiversity is not represented by a single taxon, because the correlation in assemblage similarity between the taxonomic groups was low. Considering ecological sensitivity, sampling effort (=number of samples and necessary site visits), taxonomic stability and state of knowledge on species' habitat requirements, we therefore suggest the inclusion of ground-dwelling spiders, oribatid mites and vegetation in an ecological assessment system for peatlands, complemented by a few sensitive, easy to recognize indicator species of other taxonomic groups.
... The mowing had a positive effect on the floral diversity (Buttler 1992, Güsewell et al. 1998, the richness of the growing plant species gives diverse habitat structure, therefore the number of spider species increases as well. (Zschokke 1996;Tews et al. 2004;Malumbres-Olarte et al. 2013). These statements are supported by our data because the species richness and the number of individuals were higher in hay meadows. ...
Our investigation targeted the diversity of spider communities of meadows under nature conservation management and the relationship between mowing and the spider diversity. The study sites represented by six grasslands on three localities of Mátra mountain of Hungary. All three localities were contained a hay meadows and a not mowed meadows. Hay meadows had the richest spider communities. In the control habitats, the equitability and the Shannon-Wiener diversity were lower than in the mowed grasslands. According to the Bray-Curtis similarity index significant differences were observed between spider assemblages of mowed and control habitats. The prevention of succession effects so rich structure of the vegetation where diverse spider communities can live. Our results suggest that mowing is a suitable management for maintaining a high biodiversity in mountain grasslands.
Spider webs in general and orb webs in particular are delicate, ephemeral structures that are frequently damaged in nature. Some orb weavers respond to damage by quickly shoring up their webs with non-sticky dragline silk. This study of how Micrathena duodecimspinosa (O. Pickard-Cambridge, 1890) shores up damaged frame lines shows that repairs were largely based on a single, repeated pattern of attachments. These movements are shared with the distantly related family Pholcidae, suggesting a possibly ancient origin. Spiders tended to initiate repairs at the lower edge of a damaged sector, probably to reduce the damage produced when the spider's own weight caused sticky lines in slack portions of the web to sag into and adhere to each other. Repairs of lateral frames recuperated capture area more successfully than did those of upper frames, probably because damage caused by the spider's own weight during repair was reduced.
Wholeness of vital processes in both, internal and external dimension
is manifested, according to Aristotle’s terminology, by a substantial living form and
is a condition of a purposeful behavior.
Authors claim that, empirical data concerning animals tool use, and data
concerning regulating processes, inside every living organism, cognitively force us to
place them within teleological-holistic conceptual frames.
According to the authors, teleology requires a renewed revision and specific
defining. Although, from one hand, some researchers think that it is an adequate tool
used to describe biological purposeful processes, from the other hand it has often
been weeded out and replaced by physical concept of function. Biological
functionality intuitively links with the concept of wholeness and purposefulness. It
should be emphasized, however, that not always simply physical concept of function
may coincide with the concept of function in a biological sense, in spite of the fact
that some relations observed within a living organism might by expressed thanks to a
physical concept alone.
The main objective of this paper is to report the effect of shrub removal and mowing on the diversity and composition of ground-dwelling spider assemblages in Natura 2000 habitats of Mátra Mountains. We found significant effects of shrub removal and mowing on spider communities. Diversity decreased in the year following shrub removal but increased in the following years. Spider diversity in the final year decreased due to the lack of additional treatments. During our study the hay meadows were the most diverse habitats compared to control shrubs and treated shrubs. Treatments caused changes in community structure: the highest number of generalist species was observed in the treated shrubs, and the highest density of rare and protected species in the hay meadows. The high species turnover observed between hay meadows and control shrubs reflects the importance of grassland management. We conclude that shrub removal an effective grassland management action to increase spiders diversity in Natura 2000 habitats. Finally, treated shrubs require additional treatments such as mowing to ensure the spider communities inhabiting them are as diverse as those inhabiting meadows.
The life history of any animal is greatly influenced by three factors (Stearns 1976): the need to grow and reach maturity, the need to feed in order to accumulate the energy necessary for growth, and finally, the need to reproduce. Reproduction is often seasonal, and often the reproductive success depends greatly on body size and physical fitness (Thornhill and Alcock 1983). Hence, the effectiveness of foraging, the efficiency of growth and the timing of maturation all directly affect reproductive fitness. Accordingly, we would expect natural selection to have sharpened the animal’s process of making optimal decisions regarding foraging and growth.
A relative measure of predation on web-spiders was determined for temperate (Pennsylvania, USA), subtropical (Peru), and tropical (Gabon) forests. Predation was quantified by comparing the losses of matched individuals in 4 treatment groups. Spiders in groups 1 and 2 were released on natural vegetation in the forest. Group 3 spiders were released in complete cages. The number of spiders lost from groups 1, 2 and 3 during the daytime on the 2 tropical sites was significantly higher than losses in group 4 or during any other time period. Results might indicate that predation, at least by vertebrates, is more intense during daytime periods on those tropical sites.-from Author
SYNOPSIS. Sensory events presumably guide the orb-weaver in the sequence of placing radii. However, at a given stage of construction, several sectors of the web may be equivalent in the sense that they possess features capable of eliciting radius-building. Observation of the natural progress of construction cannot reveal these characteristics. Some delineation of the problem may be obtained by compelling the spider to identify equivalent sectors. This procedure was followed for Araneus diademntus by selectively destroying threads, in effect repeatedly forcing the spider into the same web-array. The “candidate” sectors—those regions which are placed and replaced by the spider—are sufficiently described by the size of their central angles in early stages of radius-building, but not in later stages. Angles of relatively large size are left open in the upper half of the web. Sensory guidance in construction of radii may depend upon response to a complex array of forces in the web.
Aus: Zeitschrift f. Morphologie u. Ökologie d. Tiere. Bd 36, H. 2. Münster, Phil. u. naturwiss. Hab.-Schr., 1939 (Nicht f. d. Austausch.).
The uloboridPhiloponella vicina differs from the araneoids Nephila clavipes and Leucauge mariana in one movement made during frame construction, in the ordering of frame construction, in proto-hub removal, and in the highly ordered sequence of operations on adjacent radii just before proto-hub removal. Data from other uloborids suggest that all of these differences may distinguish orb weaving uloborids in general from orb weaving araneoids .N. clavipes differs from the other two species in the order of lines laid during frame construction, in the high variability in the details of frame construction, and in its failure to remove recently laid lines during exploration, radius construction, and frame construction. Frame construction behavior in all three species is more variable than previous reports indicated, and more variable than behavior in later stages of orb construction . In all three species earlier frame construction more often involves breaking lines already present in the web . Similarity between uloborid and araneoid frame construction is more likely to be due to a combination of constructional constraints and inheritance of ancient spinning patterns than previously realized ; it is not clear whether or not it constitutes a synapomorphy uniting the two groups . The failure of N. clavipes to remove recently laid lines during exploration, radius construction, and frame construction is probably plesimorphic . Secondary loss of removal behavior seems unlikely because removal probably confers adaptive advantages . Removal behavior in these contexts and possibly more stereotyped frame construction behavior probably evolved independently in uloborids and araneoids .
Pretensile forces were measured in individual threads of intact spider webs. In the orb web of Araneus diadematus forces decrease from mooring threads to frame threads and radii, a typical ratio being 1071. The smaller number of radii in the upper than in the lower half of the orb is paralleled by force ratios of 21 to 31. A similar difference between radii built first during web construction and radii added after completion of the frame underlines the importance of the former as part of the scaffolding. High tensions in the auxiliary spiral stabilize the radii in addition to providing a pathway for the spider when inserting the sticky spiral. Radial pretension (F) changes with spider mass (m). F/m is similar for different animals indicating an adaptation of radial forces to those resulting from spider mass. Several observations suggest tension control by the spider. When forced to anchor its web to thin flexible rods tension in the threads remains in the normal range. Tension values are similar in the webs of A. diadematus, Zygiella x-notata, Nuctenea umbratica, and Nephila clavipes indicating independence from details of web geometry. Only the mooring threads of Nephila show unusually large forces suggesting a narrower working range of tensions for the catching area than for the scaffolding.
Beobachtungen libe r den Bau des Netzes der Kreu zs pinne (Aran ea diadema L.). Travaux de l 'lnstitut de
- E Petrusew Iczowa
PETRUSEW ICZOWA, E. 1938. Beobachtungen libe r den Bau des Netzes der Kreu zs pinne (Aran ea
diadema L.). Travaux de l 'lnstitut de Biolog ie Gemirale de l'Universite de Vilno 13: 1-24.