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Observation on the biology of Caraphractus cinctus (Walter) (Hymenoptera: Mymaridae), a parasitoid of the eggs of Dysticidae (Coleoptera). III. The adult life and sex ratio
... For example, in the species Caraphractus cinctus Walker (Mymaridae), females oviposit submerged and place its eggs inside the eggs of other insects, preferably of Dytiscidae beetles. However, when lacking aquatic hosts, females may leave the water to search for potential organisms and lay the eggs flying towards the marginal vegetation (Jackson 1958(Jackson , 1966. Jackson (1961Jackson ( , 1963Jackson ( , 1966) made a thorough description on the biology of this mymarid. ...
... However, when lacking aquatic hosts, females may leave the water to search for potential organisms and lay the eggs flying towards the marginal vegetation (Jackson 1958(Jackson , 1966. Jackson (1961Jackson ( , 1963Jackson ( , 1966) made a thorough description on the biology of this mymarid. He dem-onstrated that mating (lasts about 10 s) occurs under water in the majority of times; males (which emerge first) wait for females to hatch from the eggs of the host, then raise the wings vibrating it, and then mount the female remaining on the top, curving its abdomen to reach female genitalia. ...
... Males may wait for several females to emerge and then mate with them subsequently. Females can also be parthenogenetic, laying eggs almost immediately after emergence (Jackson 1966). After mating, females actively search for the eggs of potential hosts under water, often placed under leaves (Jackson 1963(Jackson , 1966. ...
Aquatic insects present diverse reproductive strategies, tactics, and complex life cycles which require distinct amounts of space and different food sources. And to achieve the reproductive goals they make use of many other strategies. Such reproductive repertoire allowed these insects to evolve the most intricate and fantastic mating systems, often involving conspicuous ornaments. This chapter treats some of these subjects, providing examples from studies carried out worldwide with aquatic insect orders, approaching differences among males and females, sex ratio, sex maturation, reproductive strategies, and all aspects that are involved in success or failure of the competitors. In the first part of this chapter, we treat all insect orders that are aquatic (complete cycle under the water) and semiaquatic (larval stage under the water), mentioning the life cycles and some reproductive tactics. In the second part, we discuss about the theoretical approach concerning insect reproduction such as sexual selection, trade-offs, and roles of polymorphism.
... Species of Mestocharis are documented as parasitoids of Dytiscidae eggs (Coleoptera) with European species known as solitary or gregarious (1993) endoparasitoids (Boucek et al. 1963, Jackson 1964), but there is no specific record for M. tropicalis (Yoshimoto 1976 Jackson (1956Jackson ( , 1958 recorded Mestocharis bimacularis (Dalman) from eggs of Dytiscus marginalis L., as well as Dytiscus circumflexus Fabricius and Dytiscus semisulcatus Mü ller, and detailed its biology (Jackson 1964). Jackson (1966) illustrated and described dytiscid eggs that served as host to a mymarid wasp. Our remains are similar in size and coloration to those reported in Jackson (1966) but, unfortunately, our host identification is equivocal. ...
... Jackson (1966) illustrated and described dytiscid eggs that served as host to a mymarid wasp. Our remains are similar in size and coloration to those reported in Jackson (1966) but, unfortunately, our host identification is equivocal. ...
The results of a survey of parasitoid wasps associated with herbivorous insects on Sagittaria latifolia Willd. and Sagittaria platyphylla (Engelm.) J. G. Sm. (Alismatales: Alismataceae) in the Nearctic Region are reported. The following 10 wasp species were reared from insects on S. platyphylla: Gonatocerus sp., Mestocharis tropicalis Yoshimoto, Syntomopus americanus Ashmead (all Chalcidoidea), Hexacola websteri (Crawford), Rhoptromeris sp. (both Cynipoidea), Alabagrus texanus (Cresson), Bracon sp. nr. mellitor Say, Cotesia diacrisiae (Gahan), Enicospilus glabratus (Say), and Opius (Tolbia) hoffmanni (Fischer) (all Ichneumonoidea). Three wasp species, S. americanus, Chaenusa psillosae Kula (Ichneumonoidea), and B. sp. nr. mellitor, were reared from insects on S. latifolia. All species except C. psillosae are reported as associated with a species of Sagittaria for the first time. Mesochorus discitergus Say is reported as a hyperparasitoid of C. diacrisiae for the first time and is also reported as associated with a species of Sagittaria for the first time. Opius (Tolbia) hoffmanni is reported as a parasitoid of Hydrellia sp. prob. nobilis (Loew); this is the first record of O. (T.) hoffmanni from a species of Hydrellia Robineau-Desvoidy (Diptera: Ephydridae). Mestocharis tropicalis, S. americanus, and O. (T.) hoffmanni are reported from Louisiana for the first time. Syntomopus americanus and O. (T.) hoffmanni are reported from Texas for the first time.
... Two general kinds of definitions exist. One considers the consequences of the act: the situation which arises when females of one species deposit more eggs in or on a host than can develop to be- come adults [Salt, 1934;Fisher, 1961;van Lenteren, 1981] or more eggs than can develop to become adults of some 'optimal' size [Jackson, 1966]. The other considers the act itself: the allocation of one or more eggs to previously parasitized hosts (i.e., hosts into which one or more eggs had previously been laid) by another, conspecific female. ...
... In all experiments, Trichogramma evanescens laid on average a smaller clutch in parasitized hosts than in unparasitized hosts. This phenomenon has been found in several studies of conspecific superparasitism in gregarious parasitoids [Wylie, 1965;Jackson, 1966;Holmes, 1972;Ikawa & Suzuki, 1982;Suzuki et al., 1984;Ikawa & Okabe, 1985]. ...
Superparasitism is a widespread phenomenon in insect parasitoids and may be advantageous in certain circumstances. In this paper, we distinguish two kinds of superparasitism with different adaptive consequences for an ovipositing parasitoid: self superparasitism, where a parasitoid oviposits in a host in which she has previously oviposited, and conspecific superparasitism, where she oviposits in a host containing egg(s) from a previous oviposition by a conspecific. Our studies on Trichogramma evanescens Westwood show that females lay smaller clutches on parasitized than on healthy hosts but make the same overall allocation of males and females, although the sequence of sexes during oviposition differs. No difference was found between allocation in self and conspecific superparasitism. These results are discussed in the light of theories for progeny and sex allocation.
... Interestingly, the host orders for the above three genera are different: Orthoptera, Psocoptera, and Coleoptera. It is assumed that all these cases involve gregarious parasitism but likely not superparasitism or multiple parasitism, though see Jackson (1966) for examples of the latter. For species of Litus and Platystethynium, the host eggs are huge relative to the size of the parasitoids so large numbers of individuals develop in a single egg. ...
Platystethynium (Platypatasson) earlyi Huber, sp. n. (Hymenoptera: Mymaridae), is described from both sexes reared from an egg of Rhaphidophoridae (Orthoptera) found in an old mining tunnel in New Zealand. The male is micropterous and has lateral ocelli but no median ocellus, a unique feature in Mymaridae found so far only in males of Platystethynium Ogloblin species. The remaining described Eastern Hemisphere species of Platystethynium are discussed and Platystethynium glabrum Jin & Li, syn. n., is placed in synonymy under P. onomarchicidum Ogloblin. A key to females, and males where known, of the described Eastern Hemisphere species of Platystethynium is given.
... Smaller females and those with shorter life spans will produce fewer progeny of their own (van Driesche & Murray, 2004). Different studies on parasitoid species have found male-biased sex ratios in Gregopimpla himalayensis (Hymenoptera: Ichneumonidae), Nasonia vitripennis (Hymenoptera: Pteromalidae) and Caraphractus cinctus (Hymenoptera: Mymaridae)) (Godfray, 1994;Holmes, 1972;Jackson, 1966;Shiga & Nakanishi, 1968;Tagawa, 2000;Walker, 1967;Wylie, 1965Wylie, , 1966. Smith (1996) reported that in Trichogramma spp., a high female-to-egg host ratio favours superparasitism but has the negative impacts associated with male-biased and low quality offspring. ...
The encyrtid Ooencyrtus kuvanae is a solitary parasitoid of the gypsy moth, Lymantria dispar L. (Lepidoptera-Lymantridae) that is used in biological control programmes and whose mass rearing is influenced by superparasitism. The purpose of this study was to investigate the effect of the self-superparasitism of O. kuvanae at different host densities (5, 10, 15 and 20), female ages (3 and 5 days) and durations of exposure (1 and 5 days) under various laboratory conditions (25°C ± 1°C, RH 60 ± 5% and a 16:8 h light:dark photoperiod) as well as in a new laboratory host, Philosamia ricini (Danovan) (Lepidoptera: Saturniidae) of O. kuvanae. In this study, we determined the rate of egg superparasitism and adult emergence and recorded development time, longevity and body weight. Superparasitism increased with female age and the duration of exposure to parasitoids when females had access to five host eggs. Superparasitism increased the number of parasitoid offspring, but it resulted in male-biased (56.90%) progeny. Furthermore, superparasitism caused deleterious effects to the fitness of the progeny by prolonging the developmental process, and decreasing longevity. For example, we found that when four adults can emerge from one superparasitised host egg, the body size of the parasitoid offspring decreases significantly. Hence, superparasitism should be avoided when mass rearing O. kuvanae.
... Huber (1986) published a review of the hosts of mymarids and also stated that they particularly parasitize eggs in concealed situations such as those embedded in plant tissues, placed under scales, bracts or in soil. Few mymarids are also capable of swimming under water in search of their aquatic insect egg hosts, using their wings as oars (Matheson and Crosby, 1912 and Jackson, 1966). Indian mymarid taxonomy was mainly studied from Aligarh Muslim ...
A survey was conducted between February and March, 2011 to collect mymarid parasitoids from forest ecosystem from Pudhucherry (Pondicherry University premises) and orchard and weed ecosystem from Pandit Jawaharlal Nehru College of Agriculture (PAJANCOA), Karaikkal using two collection methods (net sweep, and yellow pan trap). The survey revealed new distributional records of seven genera and nine species of mymarids from Pudhucherry. Fairyflies (Hymenoptera: Chalcidoidea: Mymaridae) are internal, primary parasitoids on insect eggs especially Hemiptera, but eggs of Lepidoptera, Odonata, Coleoptera and Psocoptera are also attacked. Huber (1986) published a review of the hosts of mymarids and also stated that they particularly parasitize eggs in concealed situations such as those embedded in plant tissues, placed under scales, bracts or in soil. Few mymarids are also capable of swimming under water in search of their aquatic insect egg hosts, using their wings as oars (Matheson and Crosby, 1912 and Jackson, 1966). Indian mymarid taxonomy was mainly studied from Aligarh Muslim University (AMU), Uttar Pradesh by Verma (1980), Subba Rao and Hayat (1983), Hayat (1992), Zeya and Hayat (1995), Hayat and Anis (1999a, b, and c), Hayat and Singh (2001), Hayat et al. (2008), Rehmat et al. (2009) and Zeya (2011). Recently, in South India, the mymarid fauna of Kerala, Andhra Pradesh and Tamil Nadu was studied by Rameshkumar et al. (2011 a and b) and Manickavasagam and Rameshkumar (2011) respectively. In continuation, the mymarid fauna of puducherry is documented in the present study, as only three species (Gonatocerus meghalayanus (Zeya and Hayat, 1995), Polynema brevicarinae and P. mendeli (Hayat and Anis, 1999c) of mymarids are reported from Pudhucherry (=Pondicherry).
... In accordance to our study, findings by Boulton et al. [56] have also provided evidence to suggest that interference by male parasitoids (mating and/or harassment) during oviposition phase can completely disrupt facultative sex allocation, resulting in a less female-biased sex ratio because of female parasitoid inability to fertilize eggs. This is also similar to what was observed in Caraphractus cinctus (Walter) (Hymenoptera: Mymaridae) and Nasonia vitripennis (Hymenoptera: Pteromalidae), with the production of more male offsprings in the progeny in response to the frequency of physical and/or olfactory interference with other female (s) at the ovipositing sites [57,58]. Our findings have major implications for field releases of the parasitoids, since interference by the ants during the oviposition phase strongly influences the production of a more male-biased sex ratio. ...
The ant Oecophylla longinoda Latreille forms a trophobiotic relationship with the invasive mealybug Rastrococus iceryoides Green and promotes the latter's infestations to unacceptable levels in the presence of their natural enemies. In this regard, the antagonistic interactions between the ant and the parasitoid Anagyrus pseudococci Girault were assessed under laboratory conditions. The percentage of parasitism of R. iceryoides by A. pseudococci was significantly higher on "ant-excluded" treatments (86.6% ± 1.27%) compared to "ant-tended" treatments (51.4% ± 4.13%). The low female-biased sex-ratio observed in the "ant-tended" treatment can be attributed to ants' interference during the oviposition phase, which disrupted parasitoids' ability to fertilize eggs. The mean foraging time, host handling time and number of successful oviposition in "ant-excluded" treatment were significantly higher compared to "ant-tended" treatments. When ant workers were allowed access to sterilized sand grains, mummified and unmummified R. iceryoides, they selectively removed the mummified mealybugs, indicating that they recognized the mummies as potential foods (1.2 ± 0.46 to 7.8 ± 1.17 mummies at 10 min intervals for 2 h). Percentage emergence from mummified R. iceryoides removed by the ants was significantly lower compared to emergence from mummies not exposed to ants. Although, host seeking parasitoids frequently evaded attacks, some were killed by the foraging ant workers (2.0 ± 0.38 to 6.0 ± 0.88 at 10 min intervals for 2 h). These results suggest for the first time that the presence of O. longinoda has a detrimental effect on the abundance, reproductive success and possibly oviposition strategy of female parasitoids, which might be a delimiting factor in field conditions if both natural enemies are to be recommended for use within the same agro-ecosystem.
... Generally, parasitoid females adjust the production of males and females in order to maximize their fitness (King 1987, Leberton et al. 2010. For instance, changes in host density influence offspring sex ratio in the parasitoid Caraphractus cinctus Walker, where females deposit more female eggs when a single host is constantly offered, than when egg hosts are offered in batches of three eggs every five days (Jackson 1958(Jackson , 1966. Different cues emanated from host and conspecifics play an important role in offspring sex ratio assignations. ...
Parasitoid reproduction is often limited by disposable time for accessing hosts or egg availability. In the case of synovigenic parasitoids (which mature eggs during their lifetime), theory predicts that egg limitation is infrequent because they are able to replenish their egg supply throughout life. However, this theory does not contemplate the effect of superparasitism on egg load. If superparasitism is applied as a strategy for modulating offspring sex ratio, as extra eggs are normally deposited in each host, it is to be expected that females experience egg limitation, especially when host density is high. In this article, the effect of host density on egg load, oviposition, and sex ratio in the tephritid parasitoid Diachasmimorpha longicaudata (Ashmead) was investigated. Specifically we analyzed the rate of oviposition per host and adjustments in offspring sex ratio in response to changes in host density and how these affect egg load. Parasitoids maintained a similar rate of oviposition, independent of host densities, except when host density fluctuated between 25 and 5 hosts per day. Females increased their oviposition rate and parasitism when confronted with 5 hosts, after having experienced a density of 25 hosts. Offspring sex ratio was biased in favor of females at high host density and with increasing prevalence of superparasitism. Results suggest that parasitoids have a strategy for maintaining high egg load in order to mitigate egg limitation, and for adjusting oviposition rate and offspring sex ratio with reference to previous oviposition experience.
... However, very few parasitic Hymenoptera are fully aquatic and able to immerse completely to reach submerged hosts. Some notable exceptions are the platygastroid genera Tiphodytes Bradley (Spence 1986) and Thoron Haliday (Masner 1972;Johnson and Masner 2004) that parasitise the eggs of Gerridae and Nepidae respectively, the mymarid Caraphractus cinctus Walker that parasitises the eggs of Dytiscidae (Jackson 1966), and the ichneumonid Agriotypus gracilis Waterson that is ectoparasitic on caddisfly larvae (Aoyagi and Ishii 1991). ...
The platygastroid wasp Echthrodesis lamorali has been of considerable interest since its description in 1968, primarily because of its highly modified, densely pilose, wingless body, its distribution and unusual biology. The species is endemic to the Cape Peninsula, South Africa, where it is an endoparasitoid of eggs of the marine spiders Desis formidabilis (Desidae) and Amaurobioides africanus (Anyphaenidae) in the intertidal region. Although a highly aberrant monospecific genus, the phylogenetic relationships of Echthrodesis are confused, in part due to convergence in body form across numerous unrelated platygastroid genera. We used sequence data from the nuclear 28S rRNA and 18S rDNA genes, and the mitochondrial cytochrome oxidase 1 (CO1) gene, to determine the phylogenetic affinities of E. lamorali.We present a revised taxonomic description for the genus and species, as well as new morphological information on the structure of its mouthparts and ovipositor system. Phylogenetic analyses of molecular data place E. lamorali within one of two independent clades of platygastroid wasps that use spider eggs as hosts. Echthrodesis is sister to a group of three genera: Neobaeus (New Zealand; host unconfirmed); Mirobaeoides (Australia; spider eggs); and Embidobia (near cosmopolitan; embiid eggs). Details on the biology, behaviour and morphological adaptations of E. lamorali are provided.
... Poniżej omawiam krytycznie dwie takie publikacje, których powstanie było związane istnieniem w Puławach w latach 1869–1914 rosyjskojęzycznej, wyższej szkoły rolniczej: Instytutu Gospodarstwa Wiejskiego i Leśnictwa (IGWiL). Heteroptera) (BETTEN 1951; JACKSON 1966) – więc takie rozumowanie nie jest uprawnione. Dlatego należy odrzucić pracę ZAÏCEWA (1908) jako źródło danych o ważkach Polski. ...
Author discusses two Russian papers with data from the vicinity of Puławy (eastern Poland) which have been omitted in odonatological literature so far including “A distribution atlas of dragonflies (Odonata) in Poland”.
ZAITSEV (1908) gave on the margins of the paper about interesting insects of the vicinities of Puławy the information about the recording of Caraphractus cinctus (Hymenoptera: Mymaridae). Then it was wrongly regarded as a specialized parasite of the eggs of Calopteryx virgo therefore its presence was treated as an evidence for the occurrence of this dragonfly species. However, C. cinctus parasitizes mainly Dytiscidae (Coleoptera), it is also found in the eggs of Notonecta spp. (Hemiptera: Heteroptera) – therefore this reasoning is unauthorized and the paper of ZAITSEV (1908) should be excluded as a source of data on dragonflies of Poland.
KOLOSOV was known as the author of the paper about the mass migration of Libellula quadrimaculata through Puławy. His collection was partially preserved in the Museum and Institute of Zoology of the Polish Academy of Sciences (MIZ PAS). This data has been used by BERNARD et al. (2009) and discussed in details by BUCZYŃSKI (2012) who considered it in most as unpublished. However, it was published in „Zapiski Novo-Aleksandriyskago Instituta Selskago Khozyaistva i Lesovodstva” („Memoires de l’Institute Agronomique et Forester à Nowo-Alexandria”) (KOLOSOV 1916) although this work has never been cited, not only in Poland but also in Russia and the Soviet Union. This probably resulted from a chain of unfortunate events. The paper was published during the war when the publishing institute was evacuated from Puławy to Kharkov where it stayed. Therefore this paper was absent in Polish libraries. However, for Russian authors the discussed paper was not interesting then for it was local and referred to a different country.
KOLOSOV (1916) gave 41 dragonfly species: 40 from Puławy and its vicinity as well as 5 from fragmentary studied sites in other areas of Poland. At the same time Orthetrum cancellatum was wrongly recorded: the provided picture of copulatory apparatus of a male indicates O. albistylum. The analysis of data and the comparison with the preserved material (BUCZYŃSKI 2012) show that the specimens in MIZ PAS were reabelled which resulted in the loss of the detailed data about the sites: new uniformed labels provided general site „Novaya Aleksandriya” (=Puławy). Moreover, the collection of MIZ PAS contains the species which were not given by KOLOSOV (1916): Lestes virens, Enallagma cyathigerum, Anax imperator and A. parthenope. Taking into consideration all of the data, in the area of Puławy ca. 100 years ago 44 dragonfly species were recorded – that number was impressive in the light of contemporary standards of faunistic studies and such a small area. This shows the very high natural values of the valley of the middle River Vistula at that time. This data show the unique, almost complete picture of dragonfly assemblages of the valley of large lowland river in Central Europe during the period when such areas were still transformed
in small degree by man.
... Parasitoids generally avoid larval competition by discriminating between parasitized and unparasitized hosts and by laying eggs in unparasitized hosts (Werren 1980; van Alphen et al. 1987; van Dijken & Waage 1987; King 1993; Miura et al. 1994). Females discriminate hosts by detecting marking pheromones deposited by previous ovipositing females outside the host (Salt 1937; Rabb & Bradley 1970; Vinson & Guillot 1972; Bosque & Rabinovich 1979) or by internal marks or changes in the host (Jackson 1966; Fisher & Ganesalingam 1970; Greany & Oatman 1972; Chow & Mackauer 1986). When superparasitism occurs, the emerging clutch size and sex ratios can be different from what was laid by the first female. ...
Haplodiploid Hymenoptera females control the sex of their progeny, and
their sex allocation is influenced by several factors. The impact of intra- and
interspecific competition and of inbreeding and outbreeding on sex allocation has
been studied in some species of the egg parasitoid Trichogramma. The pre-mating
dispersion has also been studied.
Impact of competition on sex allocation was observed for Trichogramma
minutum Riley and Trichogramma pintoi Voegele. These species were chosen
because of the ease with which than can be distinguish. Results show that females
of both species lay more males under intraspecific competition than alone,
following the Local Mate Competition theory, while only T. pintoi modifies its
sex ratio under interspecific competition. Multiparasitism and natural habitat
could explain this shift in the sex ratio.
Trichogramma minutum, T. pintoi and Trichogramma evanescens
Westwood pre-mating dispersion show that most matings occur at the emergence
site. However, the three species have a potential for off-patch mating, allowing
genetic exchange between sub-populations. These three species were chosen
because they are classified in different groups in the genus.
Finally, T. evanescens did not modify its sex ratio following inbreeding or
outbreeding. The incapacity to discriminate between kin and non-kin, insufficient
genetic distance in outbreeding, or the population structure could explain these
results.
... In addition, with the presence of other mothers, the advantage to producing daughters as mates for her sons also decreases because now those daughters can become mates for the other mothers' sons. LMC may seem to be supported for many parasitoid wasp species (King 1993): consistent with LMC, overall sex ratios are often female-biased (Clausen 1939; Waage 1982; Luck et al. 1993 ); and the female-bias often decreases in the presence of other females or hosts parasiti-zed by other females (Salt 1936; Jackson 1966; King 1993 ). However, note from the dates of these publications that these empirical patterns had been demonstrated prior to, and are cited in, the first LMC paper (Hamilton 1967). ...
Maternal manipulation of offspring sex ratio in response to conspecifics is considered in relation to sex ratio theory using the parasitoid wasp Spalangia endius. Females produced a greater proportion of sons in response to mated but not virgin females. This is the first demonstration of a differential sex ratio response to virgin versus mated females and provides support for local mate competition theory. More recent sex ratio models that predict sex ratio responses to conspecifics, specifically constrained, perturbation, and crowding models, were not supported. An increased proportion of sons in response to another mated female occurred on the second day of oviposition but not on the first, and the day effect resulted from experience not age. When females oviposited alone after 2 days' exposure to another female, they still produced a greater proportion of sons than if they had always been alone, but only if the other female was mated, not if she was virgin. Females do not seem to assess the presence of virgin versus mated females indirectly by using a low density of males or a long latency to mate as an indicator for virgin females: neither affected offspring sex ratio. That mated females adjusted their sex ratios in response to other mated females, but not virgin females or males, may be due proximally to mated females not often encountering the latter. Virgin females and males are not located as deep in the oviposition substrate as mated females.
Sex allocation is defined as the allocation of resources to produce male and female offspring during reproduction, and it is an important topic in evolutionary biology. As organisms with special haplo‐diploid sex determination, parasitoid wasps are particularly suited for the study of sex allocation. However, most studies focused on the secondary sex ratio (i.e., the eclosion sex ratio) because the oviposition ratio (the primary sex ratio) is difficult to study, especially in parasitoid species. The primary sex ratio may differ from the secondary sex ratio due to larval mortality and self‐superparasitism. The present study used microsatellites to explore the effects of female age on the primary and secondary sex ratio (male proportion) of the solitary ectoparasitoid Pachycrepoideus vindemmiae (Rondani) (Hymenoptera: Pteromalidae). The primary sex ratio showed a significant decreasing trend as the oviposition days increased, and the secondary sex ratio significantly increased. Self‐superparasitism, i.e., laying more than one egg in a host, was the cause of the variation in the secondary sex ratio in P. vindemmiae. When females practiced self‐superparasitism, they tended to lay female eggs. The application of microsatellites helped explore and improve the understanding of the primary sex ratio and self‐superparasitism in this ectoparasitoid species.
The distribution and diversity of aquatic insects is a result of their interactions with the environment and other organisms. Right from the egg to larval and adult stages, insects must deal with a great biodiversity of natural enemies and mutualists. Such relationships evolved for millions of years in such a way that aquatic insects developed behavioral, ecological, and evolutionary strategies to cope with predation, parasitism, and competition. In the same way, they have joined forces with other organisms to solve problems, such as the interaction with gut bacteria to digest cellulose. These strategies and selective forces not only predict behavior and occurrence of aquatic insects, but also shape their diversity, community structures, and population dynamics. In this chapter, we sought to bring to the reader a useful source of information and a background for future studies. Although our current knowledge on species interactions in freshwater habitats allows us to discuss several topics, there is an open field of possibilities and gaps to be addressed in future research.
Supplementary material for ‘Mate limitation and sex ratio evolution’: Data for Fig. 1, and additional mathematical derivations.
A faunistic survey was conducted to collect mymarid parasitoids from different ecosystems using three collection methods (net sweep, yellow pan trap and Malaise trap) in selected districts of Kerala. The survey revealed the presence of 14 genera and 29 species of mymarids of which 11 genera and 11 species are new distributional records for Kerala.
Recent decades have witnessed an explosion of theoretical and empirical studies of sex allocation, transforming how we understand the allocation of resources to male and female reproduction in vertebrates, invertebrates, protozoa, and plants. In this landmark book, Stuart West synthesizes the vast literature on sex allocation, providing the conceptual framework the field has been lacking and demonstrating how sex-allocation studies can shed light on broader questions in evolutionary and behavioral biology. West clarifies fundamental misconceptions in the application of theory to empirical data. He examines the field's successes and failures, and describes the research areas where much important work is yet to be done. West reveals how a shared underlying theoretical framework unites findings of sex-ratio variation across a huge range of life forms, from malarial parasites and hermaphroditic worms to sex-changing fish and mammals. He shows how research on sex allocation has been central to many critical questions and controversies in evolutionary and behavioral biology, and he argues that sex-allocation research serves as a key testing ground for different theoretical approaches and can help resolve debates about social evolution, parent-offspring conflict, genomic conflict, and levels of selection. Certain to become the defining book on the subject for the next generation of researchers, Sex Allocation explains why the study of sex allocation provides an ideal model system for advancing our understanding of the constraints on adaptation among all living things in the natural world.
(1) A simple model is presented to describe the egg distributions of solitary insect parasitoids. (2) The model, which can be fitted by use of a small desk calculator or even a slide rule, assumes that parasites encounter their hosts at random, and avoid superparasitism during a fixed proportion of re-encounters. (3) The model successfully describes the egg distributions of twenty-five species of both internal and external solitary parasitic Hymenoptera. Calculated average avoidances for the egg distributions of all the species are given in a table. (4) In some species the proportional avoidance of superparasitism depends on the level of exploitation of the host population. (5) Avoidance of superparasitism, of obvious advantage to the individual parasite with a limited supply of eggs, may also be involved in parasite interference.
Twenty-three characters or character systems of adults and larvae of Terebrantes are analyzed for evidence of monophyly and phyletic relationships of Chalcidoidea, Mymaridae, and Mymarommatidae. The taxa are considered to be a monophyletic group based on 3 hypothesized synapomorphies: mesotrochanteral depressor without fu2-tr2 or mesoscutal portion of t2-tr2; axillar phragma as site of origin for all or part of t,-tr2 muscle; and independent basal ring absent from male genitalia. The family Mymaridae is considered to be monophyletic based on at least 3 apomorphies: fore wing with hypochaeta; head with frontal, median, and supraorbital sulci; and toruli distinctly closer to inner margin of eye than to each other. Chalcidoidea, including Mymaridae, is considered to be a monophyletic taxon based on 3 apomorphies: prepectus externally visible, at least dorsally adjacent to lateral edge of mesoscutum; mesothoracic spiracle positioned at exposed lateral edge of mesoscutum; and multiporous plate sensilla of antenna with unique structure, as described in text. Mymarommatidae is considered to be the monophyletic sister group of Chalcidoidea based on several apomorphies, including 4 autapomorphies: head composed of frontal and occipital sclerites, which are connected by pleated membrane along hyperoccipital region; hind wing stalk-like, without membrane and terminated in bifurcation that clasps fore wing; fore wing with reticulate pattern formed by raised lineations of membrane; and axillar portion of t2-tr2 muscle absent. Phyletic relationship of Serphitidae with Mymarommatidae is deemed inconclusive because relevant internal character states of amber fossil serphitids cannot be determined. It is suggested that mymarommatids be accorded family status, but not be assigned to superfamily until phyletic relationships are more accurately determined in Terebrantes. A matrix summarizes character-state distribution of most characters analyzed for Terebrantes, and a cladogram illustrates hypotheses of character-state evolution and proposed relationships.
The mutualism between fig trees and their wasp pollinators is a model system for many ecological and evolutionary studies. However, the immature stages of pollinating fig wasps have rarely been studied. We monitored developing fig wasps of known ages and performed a series of dissections at 24 h intervals to identify key developmental traits of Ceratosolen solmsi marchali Mayr (Hymenoptera: Agaonidae), a pollinator of Ficus hispida L. (Moraceae). We identified where in the Ficus ovary eggs were deposited and time to hatch. We were also able to identify the timing and key underlying characters of five larval instars, three sub-pupal stages, and a single prepupal stage. We provide detailed morphological descriptions for the key stages and report some behavioral observations of the wasps in the several developmental stages we recorded. Scanning electron microscope images were taken.
Females of Nasonia vitripennis cannot distinguish newly parasitized hosts from unparasitized ones but after 60 hr parasitization the parasitized puparia are rejected as oviposition sites. The sheath and stylets of the ovipositor have nerves passing down their canals leading to several types of receptor at the tip of the ovipositor shaft. Differences are detectable in the chemical composition of host haemolymph after 3 days parasitization as compared with the unparasitized condition. These may be the factors bringing about discrimination.
Pimplopterus dubius (Hymenoptera: Ichneumonidae) is a solitary endoparasitoid. It has been investigated, how the larvae of this species achieve sole occupation of the host - larvae of Epinotia tedella (Lepidoptera: Tortricidae).
The progeny of P. dubius was found to be distributed at random among the hosts, and it is discussed, whether this fact could be taken as a proof for an undiscriminating ovipositional behaviour of the female parasitoid or not.
In the superparasitized hosts, the supernumary parasitoids were eliminated by intraspecific competition. It has been demonstrated, that the winning parasitoid was the oldest of the competitors, and that it was situated in the front end of the host. Further the results here obtained, suggest, that the young parasitoids upon hatching actively migrate to the front end of their hosts, and thus put themselves in a favourable competitive position.
Finally the mechanism of competition used by P. dubius is discussed. Although it is obvious, that physiological suppression settles the competition, the nature of this suppression is unclear.
Interspezifische Konkurrenz bei Pimplopterus dubius Hgn. (Hym., Ichneumonidae), einem Parasitoiden von Epinotia tedella Cl. (Lep., Tortricidae)
Der häufigste Parasitoid von Epinotia tedella, die Ichneumonide Pimplopterus dubius, ist eine solitäre Art. Es wurde untersucht, wie es den Raupen dieser Schlupfwespe gelingt, je einen Wirt für sich allein zur Verfügung zu haben. P. dubius superparasitierte oft seine Wirte, und seine Brut war willkürlich verteilt. Es wird diskutiert, ob eine solche Verteilung als Ausdruck eines undiskriminierenden Eiablageverhaltens betrachtet werden kann. In superparasitierten Wirten wurden die überschüssigen Parasitoide durch einen intraspezifischen Kampf eliminiert. Es konnte nachgewiesen werden, daß die siegreiche Parasitenlarve sich im Vorderteil des Wines befand und daß sie wahrscheinlich die älteste der konkurrierenden Larven war. Die Ansicht wird vertreten, daß die frischgeschlüpften Larven von Pimplopterus dubius dazu neigen, in den Vorderteil des Wirts zu wandern, wenn sie sich nicht schon von Anfang an dort befinden. Endlich wird über den Mechanismus der intraspezifischen Konkurrenz diskutiert.
Females of Nasonia vitripennis (Walk.) lay a smaller percentage of fertilized (i.e. female) eggs on house fly, Musca domestica L., pupae previously parasitized by their own species, by Muscidifurax zaraptor K. & L., or by Spalangia cameroni Perk. (Hymenoptera: Pteromalidae) than on unparasitized hosts. They respond to changes in the fly pupae associated with death, and in the case of house flies attacked by N. vitripennis, to "venoms" injected at that time or to changes unrelated to death. By not fertilizing eggs that they lay on attacked hosts, the females also conserve sperm, for immature N. vitripennis on previously-attacked fly pupae are usually killed by parasite larvae already present.
A laboratory ecosystems consisting of the aphid-host, Aphis craccivora reared on Cajanus cajan, Dolichos lablab and Solanum melongena host plants and the aphidiid parasitoid, Trioxys (Binodoxys) indicus, was used to determine the searching efficiency of T. indicus in the presence and absence of male parasitoids. The searching efficiency of female parasitoids was found to decrease in the presence of their own males. Therefore, it is suggested that the effect of males should be taken into account together with other factors while constructing the life table of the parasitoid.
Zur Parasitoid-Wirt-Beziehung zwischen Trioxys (Binodoxys) indicus Subba Rao & Sharma (Hym., Aphidiidae) und Aphis craccivora Koch (Hom., Aphididae). VII. Einfluß der Parasitoiden-Männchen auf die Suchleistung in Abhängigkeit von verschiedenen Wirtspflanzen
Im Labor wurde die Beziehung zwischen Aphis craccivora, gezüchtet auf den drei Wirtspflanzen Cajanus cajan, Dolichos lablab und Solanum melongena, und Trioxys indicus untersucht, um den Einfluß der Männchen auf die Suchleistung der Parasitoiden zu bestimmen. Es konnte festgestellt werden, daß die Suchleistung der Parasitoidenweibchen in Gegenwart ihrer Männchen abnahm. Es wird daher vorgeschlagen, daß der Einfluß der Männchen, zusammen mit den anderen Faktoren, bei der Erstellung von Lebenstafeln berücksichtigt werden sollte.
The host examination behavior of the parasitoid wasp Trichogramma minutumon spherical Manduca sextahosts is described. The mean walking speed during host examination was 0.64 ± 0.03 mm s-1and is independent of wasp size. The paths taken by the wasps are not evenly distributed over the host surface; the majority of time is spent below 45 ° latitude. The distribution of oviposition sites is also nonrandom with respect to latitude and is not influenced by phototaxic and geotaxic responses. The initial transit made by the wasps over the host surface is a straight path which frequently passes across the highest point on the host. The length and duration of the initial transit are independent of wasp body length. However, stride length and stepping rates are proportional to wasp body length, and small wasps take more steps to complete their initial transit. The roles of the examination walk in host recognition and host volume measurement by Trichogrammaare also discussed.
The fine structure of the sense organs on the ovipositor of the ichneumonid Devorgilla canescens is described. These occur on both pairs of valvulae of the ovipositor but are more abundant on the second valvulae. The central lumen of the second valvula contains prominent nervous tissue terminating in groups of dendrites, each having 9 + 0 centriolar derivatives. Three such dendrites, enclosed in a common sheath, innervate each cuticular sense organ. A comparison with published descriptions of chemosensory hairs on the antennae of flies suggests that their function is similar.
Interference among females of Nasonia vitripennis (Walk.) reduced consistently though not significantly the percentage of fertilized (i.e. female) eggs that each female laid. The physical aspect of the interference apparently was responsible for part of the reduction; females whose oviposition was interrupted physically in each of six other ways also laid relatively though not significantly fewer fertilized eggs. Neither olfactory stimuli from other females of the same species, nor contact chemical stimuli left in the area earlier by these females, had any effect. Females resumed fertilizing eggs normally after the interference factor had been removed.
The question how to check the ravages of obnoxious insects is a very important one, and I am very often asked for advice in special cases. While occupied with a close examination of the proposed remedies and looking through a large number of scientific tracts, some of them fell into my hands and induced me to study them again. The present communication is the result of those studies.
Résumé L'étude du superparasitisme chez les parasites oophages desAelia a été réalisée avec 3 espèces d'Ooencyrtus: O. fecundus
Ferr. & Voeg.,O. nigerrimus
Ferr. & Voeg., etO. telenomicida
Vass. Ces 3 espèces apparaissent comme ayant un pouvoir de discrimination leur permettant d'éviter le superparasitisme lorsqu'elles
ont suffisamment d'hôtes à leur disposition. Dans le cas contraire ou lorsque le nombre de femelles dans un même tube de ponte
s'accroît, la tendance au superparasitisme augmente. Le superparasitisme se traduit par une baisse de la fécondité, une diminution
de la taille et une modification du taux sexuel de la descendance.
For organisms exploiting patchy resource landscapes, the degree of aggregation of individuals across patches has important implications for population and community ecology. For insects breeding in mushrooms, carrion, or fallen fruit, larval aggregation has previously been shown to be sensitive to the density of ovipositing females and to variation in patch quality and detectability. However, effects of resource patch density (interpatch spacing) have not been examined. I tested for an effect of patch density on larval aggregation in natural populations of mushroom-breeding flies. Larval aggregation increased strongly and consistently with declining patch density (increasing patch spacing). This effect could be due to increased aggregation of ovipositing females, but is more likely due to increased clutch sizes laid by females facing higher travel costs for movement among patches (when those patches are more distantly spaced).
Reduced oviposition by ladybirds in the presence of tracks of fourth instar larvae owing to the presence of oviposition deterring pheromones is well established across many genera. However, deterrence, if any, by other life stages has not been well investigated, in particular the effect of conspecific presence. The present study investigates the effects of conspecific presence and semiochemicals of conspecific life stages (eggs, fourth instar larvae, pupae, adult males and females) on oviposition by five ladybird (Coleoptera: Coccinellidae) species, viz. Coccinella septempunctata, Coccinella transversalis, Cheilomenes sexmaculata, Propylea dissecta and Anegleis cardoni. Results reveal that the presence of life stages inhibits oviposition and the inhibition is densitydependent, although the degree of inhibition is species-specific. Surface semiochemicals of eggs and larval and adult tracks also show density-dependent inhibitory effects. Moreover, the semiochemicals in tracks (oviposition deterring pheromones) and egg surface semiochemicals are not similar, indicating semiochemical parsimony. Of all species tested, C. transversalis and C. septempunctata were the most and the least responsive to both conspecific presence and semiochemicals, respectively.
Lorsque 2 femelles ou 3 femelles de l'ectoparasite D. vagabundus parasitent conjointement un même lot d'hôtes l'intensité du grégarisme larvaire s'accroît par rapport à celui observé en présence d'une seule femelle pondeuse. Cela se traduit par une augmentation significative du nombre moyen de descendants des 2 sexes mais la production moyenne en fils est toujours très inférieure à celle des filles. Cependant, lorsque la densité de femelles pondeuses passe de 1 à 3, le rapport des sexes mâles/femelles des descendants évolue vers l'unité traduisant une augmentation plus rapide de l'effectif des fils que des filles.
The search rate, the number of ♀ progeny per ♀ parent and the sex ratio of the progeny of Trichogrammatoidea lutea Girault were severely affected by increasing the parasite density from 1/150 hosts to 8/150. Trichogramma brasiliensis Ashmead was very little affected. Females of T. lutea were more susceptible than ♀ ♀ of T. brasiliensis to interference from other searching ♀ ♀ or by encountering hosts that had been previously parasitised. T. lutea ♀ ♀ tended to leave the area they searched following interference. T. lutea was found to be arrhenotokous and T. brasiliensis deuterotokous. T. lutea clustered its progeny in the hosts more than T. brasiliensis . The average number of T. lutea progeny that developed in a host was 2.02 as compared with 1.28 for T. brasiliensis . The clustering of ♀ progeny in the parasitised hosts by the 2 species did not differ. The average number of T. lutea ♀ ♀ per host was 1.32. When more than one progeny of a mated T. lutea ♀ developed in a host, usually only one ♀ emerged, the rest being ♀ ♀. T. lutea produced more ♀ progeny per ♀ parent than T. brasiliensis and its developmental time was shorter.
RÉSUMÉ
De certains aspects de la reproduction du Trichogramma brasiliensis et Trichogrammatoidea lutea, parasites d'oeufs d' Heliothis armigera
Les taux de prospection, le nombre de filles par femelle et le sex ratio de la descendance de Trichogrammatoidea lutea sont fortement modifiés quand la densité des parasites croǐt de 1/150 hǒtes à 8/150; par contre Trichogramma brasiliensis en est très peu affecté. Les femelles de T. lutea sont plus sensibles que celles de T. brasiliensis aux interactions avec les autres femelles en prospection ou à la rencontre d'hǒtes déjà parasités. Les femelles de T. lutea ont tendance à abandonner une zone où il y a eu rencontre. T. lutea est arrhénotoque et T. brasiliensis deutérotoque. T. lutea groupe plus ses oeufs dans les hǒtes que T. brasiliensis : 2.02 T. lutea se développent en moyenne par hǒte, contre 1.28 T. brasiliensis . Il n'y a pas de différence dans l'agrégation des filles dans les hǒtes parasités par les deux espèces: on observe en moyenne 1.32 fille de T. lutea par hǒte. Quand il y a plus d'un enfant de T. lutea accouplée par hǒte, il n'apparaǐt généralement qu'un seul fils, les autres enfants étant des filles. T. lutea produit plus de filles par femelle que T. brasiliensis et son développement demande moins de temps.
The sex-allocation behaviour of the solitary ectoparasitoid Dinarmus basalis (Hymenoptera: Pteromalidae) was investigated by examining the female's response to two proximal factors: the host-patch characteristics and the conspecific female density in the patch. The offspring sex-ratio of single females presented with unparasitised hosts was female biased (approximately three daughters to one son in the progeny) whatever the host density tested. The sex-ratio in the presence of hosts parasitised by a conspecific 48 h beforehand was male biased. The proportion of male offspring also increased when the number of conspecific females exploiting the patch changed from a single female to a group of females, whatever the group size. No sexual differences in mortality as a result of larval competition on superparasitised hosts were observed. The offspring sex-ratios observed in response to the host-patch characteristics were the result of manipulation of the egg fertilisation by the females during the oviposition phase. Thus, the variability of the sex-ratio in response to an increase in the number of conspecific females in the same patch represented a reduction in egg fertilisation. These results are analysed with regard to the predictions of Local Mate Competition theory and the females' host discrimination ability.
One ovipositing adult female D. vagabundus will give rise to three females and one male on the average. In order to test the hypothesis of the preferential death of one sex, we experimentally determined if the sex ratio at ovipositing was the same as that of the emerging adults. Newborn larvae were used after first determining that their number was the same as that of the eggs deposited. When six larvae were transferred to a paralyzed host, there was no selective elimination of larvae by competition between sexes, since all developed up to the adult stage. The sex ratio observed at emergence of the adults was thus the same as that at ovipositing.
The emission sequence of haploid and diploid eggs showed that the majority of the first eggs oviposited are fertilized, the haploid eggs being emitted last.
Mating between genetically close D. vagabundus parents occurs with 60 to 89 % of the females. The productivity of females after six generations of sibling crosses was unaffected and there was no significant change in the sex ratio of the progeny.
Résumé
Stratégie reproductive chez Dinarmus vagabundus Timb. (Hym.; Pteromalidae): taux‐sexuel réel, sequence de ponte des oeufs diploïdes et haploïdes et effets de la consanguinité sur la descendance
Chez D. vagabundus en présence d'une seule femelle pondeuse, il émerge en moyenne 3 filles pour 1 fils. Pour tester la validité d'une mort préférentielle d'un sexe sur l'autre, nous avons expérimentalement analysé si le rapport des sexes à la ponte correspondait à celui des adultes émergés. Nous avons expérimenté avec des larves néonates estimant que leur effectif correspondait à celui des oeufs pondus. Quand six larves néonates sont transférées sur un hôte paralysé, il n'y a pas une élimination sélective des larves par compétition entre sexes puisque toutes se développent jusqu'au stade adulte. Le taux sexuel observé à l'émergence des adultes correspond au taux sexuel à la ponte.
L'observation de la séquence de ponte des oeufs haploïdes et diploïdes montre que les premiers oeufs pondus sont dans la majorité des cas fécondés; l'oeuf haploïde étant pondu en dernière position.
Chez D. vagabundus , les accouplements entre parents génétiquement proches affectent de 60 à 89 % des femelles. Examinée sur 6 générations, la productivité de ces femelles n'en est pas affectée et il n'y a pas de variation significative du taux sexuel.
Zusammenfassung
Zur Reproduktionsstrategie von Dinarmus vagabundus Timb. (Hym., Pteromalidae): reales Geschlechterverhältnis, Reihenfolge der Ablage diploider und haploider Eier und Wirkungen von Inzucht auf die Nachkommen
Aus der Eiablage eines Weibchens von D. vagabundus gehen Nachkommen mit einem Geschlechterverhältnis von i.M. 3:1 zugunsten der Weibchen hervor. Zwecks Untersuchung der Hypothese über den vorzugsweisen Tod eines Geschlechts wurde experimentell geprüft, ob das Geschlechterverhältnis zur Eiablage mit jenem der Nachkommen‐Adulten übereinstimmt. Die Zahl frischgeschlüpfter Larven erwies sich als gleich mit jener der abgelegten Eier. Wenn 6 Larven auf einen paralysierten Wirt übertragen wurden, gab es keine selektive Ausschaltung von Larven durch Konkurrenz in Bezug auf die Geschlechter. Das zur Schlüpfzeit der Adulten bestehende Geschlechterverhältnis war mit jenem zur Eiablage gleich.
Die Reihenfolge der Ablage haploider und diploider Eier zeigte, daß die Mehrheit der zuerst abgelegten Eier befruchtet sind, während die haploiden Eier zuletzt abgelegt werden.
Eine Kopulation zwischen genetisch verbundenen D. vagabundus ‐Eltern kam bei 60 bis 89 % der Weibchen vor. Die Produktivität von Weibchen nach 6 Generationen Geschwister‐Kreuzungen war unbeeinflußt, auch gab es keinen signifikanten Wechsel im Geschlechterverhältnis der Nachkommen.
Abstract Using acridine orange to selectively stain eggs, we showed that wild-collected female Mediterranean fruit flies (Ceratitis capitata Wiedemann) laid fewer eggs per clutch in fruit previously infested with eggs than in uninfested fruit. This effect is apparently attributable to marking pheromone deposited by females after oviposition: clutch size on fruit infested with eggs but free of marking pheromone was not statistically different from that on uninfested fruit. Clutch size on uninfested fruit on which marking pheromone was artificially transferred was significantly lower than that on uninfested and untreated fruit. Marking pheromone had a comparable though not statistically significant effect on the clutch size of females originating from a strain maintained in the laboratory for several hundred generations.
Ecohydraulics is a relatively new name for a long-standing field investigating the interactions between ecology and the physics of flowing water. In recent decades, a burgeoning literature has developed relating species' densities to environmental variables, particularly those associated with flow. These abundance–environment relations (AERs) are sometimes used in habitat-based association models (HAMs) to predict changes to species' abundances, especially human-caused changes to the environment. Unfortunately, some conclusions arising from AERs are based on untenable ecological assertions or faulty assumptions including: illogical inference of cause-and-effect, muddling of hypotheses such as ‘habitat preference’ with other causal mechanisms, outdated ideas about environmental tolerance and optimization. Furthermore, the effects of biological interactions in AERs are routinely ignored, when biological interactions form the core of most modern models in community ecology. HAMs underpinned by AERs are often used to predict changes in populations, but lack information on demographic rates (births, deaths, migration), which are essential for population-level predictions. These weaknesses are discussed at length and, we suggest, must be acknowledged and surmounted if ecohydraulics is to advance our understanding of stream ecosystems and our capacity to manage streams. We give two examples of research at the ecological–physical interface that are grounded in ecological principles: (1) how flow influences feeding rates of filter-feeding insects (Simuliidae and Hydropsychidae) and the consequences for larval growth rates, adult body size and fecundity, and (2) how the physical factors that determine the density of rocks emergent from the water's surface may affect population densities of insects where females lay their eggs on emergent rocks. Ecohydraulics is an interdisciplinary field that requires expertise in both ecology and hydraulics, and true interdisciplinary teams may have the best prospects of addressing the many unanswered and untackled questions. Copyright © 2009 John Wiley & Sons, Ltd.
Caraphractus cinctus is an arrhenotokous mymarid parasitizing the eggs of Dytiscidae under water. In the newly emerged female only fully formed eggs are present in the ovaries and the earlier stages of ovarian development have been studied in the pupa. The two ovaries each contain from 10 to 20 ovarioles depending upon the size of the female. The two lateral oviducts unite to form the vagina which is bent upon itself when laying is not in progress. The eggs are stored in the ovarioles and the female has remarkable control over the deposition of the eggs, since in most cases she rejects host eggs already parasitized, after probing them with her ovipositor. The spermatheca is a rigid capsule and the spermathecal duct at its base has a deep U-shaped bend. There is a large spermathecal gland opening by its own duct into the spermathecal duct after the bend. The poison apparatus is well developed though the female does not kill the egg or paralyse the embryo host. The poison gland is of unusual shape being compact and rounded distally instead of tubular. Dufour's gland is large and buoyant. The ducts of both glands lead to the base of the ovipositor. The possible effect of their secretions in rendering a once parasitized Agabus egg generally unacceptable for further laying is discussed.
This study identifies some previously unreported tactile and visual cues used by the pupal parasitoid Pimpla instigatorF. (Ichneumonidae) to recognize potential hosts. Paper cylinders were presented to the wasps as simple models of lepidopteran pupae. Acceptance of these models was evaluated by determining the frequency with which the wasps punctured the cylinders with their ovipositors. The length of the cylinders did not influence acceptance of the models; however, both surface texture and structural modifications to the ends of the cylinder did affect the frequency of punctures. Smooth cylinders were punctured more often than roughened cylinders, and cylinders with closed ends were frequently punctured, whereas open-ended cylinders were consistently rejected. The wasps also discriminated between blue and yellow cylinders and could be trained to associate blue or yellow with the presence of hosts. Preferences were established during a single 90- min training period and persisted for at least 4 days following training.
Superparasitism is frequently met with in chalcids. The actual mechanism of suppression of the supernumerary individuals is
by mutual combat though exceptions to this general rule may also be seen rarely. Many chalcids are known to discriminate between
parasitised and healthy hosts. It is an interesting phenomenon that superparasitism occurs even when a female is capable of
discriminating parasitised and unparasitised hosts. Several factors play prominent roles in causing superparasitism and the
avoidance of superparasitism by a chaicid is the result of maximisation of its reproductive success.
KeywordsSuperparasitism-host discrimination-analysis-chalcids
When the effect of the kairomone, tricosane, on parasitization byTrichogramma achaeae Nagaraja and Nagarkatti of eggs ofHeliothis zea (Boddie) was studied in petri dish tests, the greatest percentage parasitization (
\mathop X_\mathop X\limits^\_
= 64%) was obtained if the entire filter paper was treated. Treatment of smaller areas (about the eggs) resulted in decreased parasitism. In the greenhouse, highest parasitization (
\mathop X_\mathop X\limits^\_
= 71%) byT. pretiosum (Riley) ofH. zea eggs placed on pea seedlings grown in pie pans was obtained if the whole pan was treated; lowest parasitism (
\mathop X_\mathop X\limits^\_
= 29%) occurred when the pans were untreated. Parasitization was intermediate (
\mathop X_\mathop X\limits^\_
= 52%) in other pans treated only at selected spots. Dissections ofH. zea eggs collected from kairomonetreated and untreated field plots revealed that eggs ofTrichogramma spp. were more efficiently distributed (less superparasitism) among host eggs in treated plots. These kairomones increase parasitization ofTrichogramma spp. by releasing and continuously reinforcing an intensified searching behavior rather than by attracting and guiding the parasite directly to the host.
The parasitic wasp Nesolynx albiclavus maintains a very skewed offspring sex ratio (ca. 4% males). We studied proximate, causal factors of the son-daughter choice mechanism to obtain insight into the precision of the procedures and the underlying rules. We analyzed the number of males in clutches produced during sessions of 12 or 24 h. The results show that the timing of the next male egg depends on the time elapsed and the number of eggs laid since the previous one. The influence of the passage of time per se during non-laying periods was reduced in an experiment with 4-h periods. The data show that the first male egg is produced by a fairly rigid process: about the sixth egg in a run will be left unfertilized. No further male egg will appear in the next 10–20 eggs if they are laid in rapid succession.
A summary of the known species of aquatic Hymenoptera is presented. In total, 150 species from 11 families are recognized
as aquatic (0.13% of the total described species). This number is likely an underestimate, because of the high percentage
of undescribed species and a lack of knowledge of host range and behaviour for most species. All aquatic Hymenoptera are parasitoids.
Many species have relatively dense pubescence to trap air and elongate, tarsal claws to grip the substrate, when underwater.
Most species are known from the Holarctic and Oriental regions, but this is likely an artefact caused by lack of knowledge
of other regions of the world. Aquatic behaviour has evolved independently at least 50 times within the order.
The parasitic wasp, Telenomus remus, lays her eggs in diserete patches of moth eggs, where her offspring develop and mate before dispersal, satisfying conditions for local mate competition (LMC). In the presence of other ovipositing females, wasps lay a higher sex ratio (proportion males), as predicted by LMC theory, and achieve this by a combination of two mechanisms, (1) avoidance of superparasitism and a sequence of sex allocation initially biased towards males and (2) a direct increase in sex ratio in the presence of other wasps, sex ratio increases with the proportion of previously parasitized hosts, as predicted by LMC theory. In both cases, chemical traces left by foraging wasps are indicated as the stimuli causing wasps to increase the proportion of males allocated to hosts.
Interspecific host discrimination by adults, and larval competition among the endoparasitoidsMicroplitis croceipes (Cresson),Microplitis demolitor Wilkinson,Cotesia kazak (Telenga) andHyposoter didymator (Thunberg) were investigated usingHeliothis virescens (F.) as the host. In ovipositional choice tests, the mean number of encounters and ovipositions for unparasitized hosts was not significantly different from the mean number of encounters and ovipositions for parasitized hosts for each treatment combination (P>0.05). Thus, none of the parasitoid species discriminated between host larvae recently parasitized once by a female of another species und unparasitized hosts. However, in all but two cases, females did discriminate between unparasitized hosts and hosts in which an early first instar of the first-attacking species was developing.Cotesia kazak andH. didymator did not discriminate between unparasitized hosts and hosts parasitized by an early first instar ofM. demolitor.
Larval competition among these parasitoid species was studied for three time intervals between the first and second species parasitization: 1) second species attack immediately (5–15 sec) after the first; 2) second species attack 24 h after the first; and 3) second species attack 48 h after the first. Time until egg eclosion was shortest forM. demolitor, thenC. kazak, thenM. croceipes, and longest forH. didymator. When the second parasitoid species attacked a host immediately after the first species, the species in which egg eclosion occurred first was the victor more frequently, except whenM. demolitor competed withC. kazak andH. didymator. With a 24 h delay between the first and second species to attack, the older first instar from the first parasitization usually outcompeted the younger first instar from the second attack. A first instar from the second species to attack generally outcompeted the second instar of the first species when the second parasitization had been delayed 48 h. Competiors were eliminated mainly by physical attack, butC. kazak andM. croceipes apparently also killedH. didymator eggs by physiological processes.
Males ofTelenomus remus
Nixon were attracted to the female by a pheromone present for the last 2 days of pupal life and the first few minutes after emergence, but not thereafter. Females in groups lived 6 times longwer than solitary ones; males did not show such a difference. Unmated males lived 8 days, and mated ones 1 day only. The normal sex ratio of 60–70 % females declined to 22 % as the females aged. Under conditions promoting superparasitism, the sex-ratio was close to 50 %. Duration of oviposition was 37 sec. with young females, but increased to over 50 sec. with age. All 3 layers of the host egg mass were parasitized equally. Several females may oviposit simultaneously on the same host batch without showing any aggression. About 60 progeny were produced during the first day of the female's life, but 20 or fewer thereafter.
A mathematical model is constructed to explain a density-dependent increase in the progeny sex ratios of gregarious parasitoids.
In the model we considered non-cooperative game between females concerned with their own inclusive fitness. Equilibrium progeny
sex ratios of the first and second females ovipositing on the same host are expressed in terms of the probability of double
parasitism (p), the ratio of a male to a female in contribution to resource competition (α), the clutch size ratio between the two females
(β), the crowding effect on female reproductive success (γ), and the inbreeding coefficient (f). Major predictions from the model are: 1) the progeny sex ratios of both the first and second females increase withp, 2) as β becomes smaller, the progeny sex ratios of the first females decrease, while those of the second females dramatically
increases, 3) when a host is attacked by at most two wasps, the sex ratio of the total number of eggs laid on the host does
not exceed 0.25. The effects of α and preferential death by female progeny in doubly parasitized hosts are considered as factors
responsible for an excess number of males at emergence. Some possible modes of density-dependent increase in the sex ratios
of the overall progeny populations is also discussed on the basis of the present model.
1. The behaviour of the Chalcid wasp Mormoniella vitripennis towards its host is described. Females previously deprived of hosts are unable to parasitize more than two hosts in 24 h. 2. The experiments of De Bach & Smith are critically re-examined. Their results are used to calculate for M. vitripennis the `area of discovery' assumed by Nicholson & Bailey to be a constant. 3. Over much of the range of host and parasite population densities studied the calculated area of discovery is reasonably constant, but falls to very low values when the host population density is high. 4. At high host population density the number of hosts attacked by each parasite is independent of host density, and the situation fits the theoretical model of W. R. Thompson more closely than that of Nicholson.
The oviposition behaviour of numerous parasites toward hosts already parasitized has been the subject of a considerable number of investigations during the past twenty years. Many species of ichneumonids, braconids and chalcids have been shown generally to avoid oviposition in parasitized hosts under laboratory and field conditions but there are conflicting views on the nature of this behiviour and on the cause for such rejection (Salt 1935, 1937, Ullyett 1936). Incomplete data hearing on these problems with the parasite Mastrus carpocapsae are given here. Dificulties in laboratory propagation and particularly irregular and erratic oviposition under the experimental techniques employed have prevented a fuller study; hut it is felt that the data will be of interest to workers in this field of behaviour since in certain respects the findings help in the interpretation of relevant facts demonstrated in previous investigations.
Among the attributes of the parasitic Hymenoptera that contribute to the ability of certain species to maintain host populations at low densities is the power to restrict egg deposition to sites suitable for the continued development of the offspring, and to regulate, regardless of host density, the number of eggs deposited per host (Flanders 1947). High searching capacity is, in part, a function of female longevity correlated with the conservation of reproductive material. It is self evident that time used in wasteful oviposition means less time for searching and consequently less effective control of the host.
Unlike most other arrhenotokous species, D. fuliginosus females cannot control fertilization of their eggs and in an optimal environment the sex ratio of any one strain is constant. Variations in the sex ratio occurred when unfavourable environmental conditions prevailed before, during and immediately following mating. Beyond half their life span, males inseminated less than half the females they mated and the inseminated females produced fewer female progeny. Temperatures above 27 °C. during post-embryonic development sterilized otherwise functional males but had much less effect on females. Structural defects of either sex were rare. Mating was successful only within the normal range for optimal adult activity. Although females were inseminated by more than one male, the sex ratio of their progeny was not affected. Larval mortality from superparasitism above 65 larvae per host differentially favoured survival of males, heightening the incidence of pairing in nature at low host population densities. The percentage females was significantly reduced when oviposition was interrupted, or delayed by low temperature, providing a possible explanation for the numerous reported differences in the sex ratio between laboratory and different geographically located populations.
1. The effect of availability of host puparis upon the sex ratio of the parasite Nasonia vitripennis has been studied.
2. When puparia are continuously available the percentage of males is 25%. When puparia are only intermittently available (for 1 hr. per day) the percentage of males increases significantly.
3. It is known that the eggs undergo resorption in females which have no access to host puparia, and it is suggested that the increase in the percentage of males is related to the increase in the number of eggs undergoing resorption in the ovarioles at the time of oviposition.
During the early part of 1932 the writer became interested in studying the life history and habits of a Chalcoid parasite of the Angoumois grain moth, Sitotroga cerealella (Olivier). The species was identified by C. F. W. Muesebeck as Habrocytus cerealellae (Ashmead). Later in the year an excellent study of the same species was published by Norman S. Noble (1). Mter reading over Noble's work, the writer decided to prepare the present paper giving briefly a part of the life history work and devoting the remainder to a discussion of certain habits of the adult. The remarkable process of oviposition seems to be specially worthy of greater emphasis. The habits of both host and parasite make them ideal material for the study of all the activities associated with oviposition.
“The reproduction of insects forms one of the most remarkable chapters in their natural history. The structural adaptations for copulation, the control of the sperm in the body of the female, the micropylar arrangements in the egg which allow fertilization through the fully formed shell, are remarkable enough. —V. B. Wigglesworth, Insect Physiology.
IT has been shown by Salt1,2 and Laing3 that the behaviour of Trichogramma in parasitizing host eggs can be divided in the following elements:
(a) The parasite makes random movements on the substrate and is visually attracted by small objects which rise above the surface.
(b) The parasite climbs up the object and spends some time in walking over its surface in a characteristic way, making intensive movements with the antennæ (here called drumming). If the object has already just been parasitized by Trichogramma, it will be rejected if the odour of the first female is still present on the chorion.
(c) After drumming, the parasite starts drilling on the surface of the object, not only on eggs, but also on small seeds and grains of sand. Odour, colour and texture of the surface of the object seem not to play a predominant part in stimulating the drilling act. The object can be rejected, however, if its measurements are such that the development of the parasite in the inside is an impossibility1.
(d) If the object is a host egg the chorion is eventually perforated and the parasite's eggs are deposited. The host is rejected after perforation, however, if it has been parasitized before2 or the embryo has reached an advanced stage in development4,5.
6. It is concluded that these spatial discrepancies do not seriously affect the numerical accuracy of the assumption that search is random in small areas, and that the theory of Nicholson & Bailey may be accurate to a first approximation.(Received August 15 1940)
Caraphractus cinctus Walker is a parasitoid of the eggs of Dytiscidae. The entire development of this Mymarid takes place in eggs immersed in water and attached to, or embedded in, plant tissue. The winter is passed in diapause as a full-grown resting larva (prepupa) in the host egg.
Diapause of Caraphractus has been studied in the eggs of Agabus bipustulatus . The eggs of this Agabus do not undergo diapause and since the shell is transparent, the larvae of Caraphractus (usually two to three in each egg) are clearly visible during their later stages, so the time of pupation is easily determined.
Experiments were made of chilling the maternal generation of Caraphractus at various stages of development, but this did not lead to diapause in the larvae of the chilled generation, or to any increase in the diapause in the offspring.
When the Mymarid was bred in a north room exposed to natural daylight and darkness, some diapausing larvae occurred in mid-September and by October all were in diapause.
When larvae were reared in long photoperiods (16½–24 hr. light) development was direct, but with short photoperiods (2–15 hr. light), diapause occurred. The critical period lies between 14 and 16 hr. of light.
The stage sensitive to photoperiod is the full-grown larva, and when larvae are reared to this stage under short photoperiod and then transferred to continuous light, direct development is determined within 3 days. Conversely, larvae reared under continuous light and removed to short photoperiod before reaching the sensitive stage, go into diapause.
The larvae are sensitive to light of very low intensity, developing direct with a ‘night’ of 0·03–0·05 f.c. Larvae becoming full grown in the end of August and beginning of September do not diapause and must respond to 2–3 hr. of twilight.
Diapause induced, under artificial photoperiods at any time of the year, usually lasts about as long as the normal winter diapause. If however the prepupae are subjected to temperatures below freezing for about a fortnight (provided they have already been about 15 weeks in diapause) pupation occurs as soon as the temperature is suitable. In cold weather the pupal stage may be greatly prolonged.
I am much indebted to Professor H. G. Callan for his kind permission to use the constant temperature rooms at the Natural History Department of St Andrews University. I have received most valuable help from Dr C. Muir in conducting the various photoperiod experiments, especially in regard to light measurements, and I am most grateful to him for discussing with me many of the problems that arose in the course of this research and for commenting on the typescript of this paper. To Dr H. E. Hinton I am indebted for useful advice, and to Dr Seliga of St Andrews University for his translation of Russian papers. Professor and Mrs Stibbs have been most kind in providing me with information regarding the duration of astronomical darkness in the latitude of St Andrews. I am especially grateful to Dr George Salt for his kindness in reading over my typescript and for his helpful criticisms.
The immature stages of Caraphractus cinctus Walker are described.
Four larval stages have been observed which may correspond to three or four instars. In no stage have mandibles been observed.
The first-instar larva is elongated and active. In the second-instar oral lobes are present. In the next stage the larva becomes shapeless and rather transparent. In the last stage the wall of the mid-gut shows conspicuous opaque spots which consist of single cells containing spherical concretions, probably the products of excretion.
These concretions later become free in the gut of the pupa and are discharged in the meconium when the imago emerges from the host egg.
The effects of parasitism on the host eggs of different ages is discussed. In newly laid host eggs all the contents are consumed by the parasitic larvae. In advanced eggs of Agabus the egg of Caraphractus is laid in the mid-gut of the host embryo where the parasitic larva develops, the hard parts of the host larva remaining intact. Parasitism in advanced eggs of Dytiscus is rarely successful.
The larvae of other Mymaridae are discussed and their main features compared. The first-instar larva of Caraphractus does not correspond to any of the previously described types of mymarid larvae.
The seasonal history is described, with the sequence of hosts parasitized throughout the year. From four to six generations of Caraphractus have been bred indoors during the year. The winter is passed as a diapausing prepupa. In some cases diapause may be prolonged. Fertility is high: 121 imagines have been bred from one female of Caraphractus .
I have much pleasure in acknowledging my gratitude to the late Dr W. D. Hincks for his kindness in reading the typescript of this paper: the comments by such a well-known authority on Mymaridae have been most valuable. I am very grateful to Mr O. Bakkendorf for allowing me to reproduce several of his figures of Mymarid larvae from the valuable work he devoted to the biology of Danish hymenopterous egg-parasites. I am also grateful to Miss B. A. Trott of the Commonwealth Institute of Entomology for the help she has so kindly given me with references.
The paper describes field and laboratory investigations on the bionomics of Cephalonomia waterstoni , a Bethylid parasite of Laemophloeus spp. A table is given in which are listed all the Bethylids attacking insect pests of stored products to which reference could be found in the literature.
An infestation of Laemophloeus , associated with two “hot spots” in Manitoba wheat, which supported a large population of Cephalonomia is described.
A simple technique for the laboratory culture of Cephalonomia is described.
The life-cycle of C. waterstoni with Laemophloeus ferrugineus as host has been worked out.
The lengths of egg, larval and cocoon (prepupal and pupal) stages at combinations of 25°C, 30°C. and 60 per cent., 80 per cent. R.H. are given. The egg and larval stages are short, lasting for about six days at 25°C. and four days at 30°C.
Within the limits used, the relative humidity appears to have no effect on the duration of development at any stage. On the other hand, temperature exerts a considerable influence; the life-cycle at 30°C. is completed in two weeks but at 25°C. it takes three weeks.
Again within the limits used, the mortality appears to increase with decrease in saturation deficit. Mortality ranged from 9 per cent, at S.D. 12·7 mm. to 36·5 per cent, at S.D. 5·0 mm.
Without food or water at all combinations of 25–30°C. and 60–80 per cent. R.H. adults live for about four days, with a range of 0·5–9·5 days. There is no difference between the sexes. Unexplained contradictory results were obtained in two experiments.
With normal or paralysed host larvae available at 30°C. and 80 per cent. R.H., males live no longer than when no food or water is available but females live for about five weeks at 25°C. and 80 per cent. R.H. and for about four weeks at 30°C. and 80 per cent. R.H.
Males fed with sucrose solution at 30°C. and 80 per cent. R.H. live for several days longer than when starved : females live for the same length of time as when fed with host larvae.
The pre-oviposition period at 25°C. and 80 per cent. R.H. is about five days; at 30°C. and 80 per cent. R.H. about one and a half days.
Fecundity. At 25°C. and 80 per cent. R.H., Cephalonomia lays about 40 eggs on 30 host larvae : at 30°C. and 80 per cent. R.H., about 65 eggs on 40 larvae.
Cephalonomia females readily oviposit on larvae that have been paralysed some time previously, and can be induced to oviposit on larvae already bearing eggs.
Virgin females produce only male offspring (arrhenotoky).
Eggs are laid in groups of one, two or three (rarely four) per larva. Single eggs produce mainly females ; pairs produce mainly one male and one female ; trios produce mainly one male and two females. At 25°C. and 80 per cent. R.H. more single eggs are laid than pairs ; at 30°C. and 80 per cent. R.H. more pairs are laid than singles. This results in the production of a higher proportion of females at 25°C. than at 30°C. The incidence of trios at both temperatures is low.
C. waterstoni is equally viable on L. minutus , L. ferrugineus and L. turcicus but shows a marked preference for L. ferrugineus .
Experiments were designed to determine the criteria by which an ovipositing female of Spalangia drosophilae Ashm. is attracted to an environment where suitable hosts may be found, and by which these hosts are selected.
The results obtained indicate that ovipositing female Spalangia are attracted to and maintained in areas where suitable host puparia may occur by their reaction to sensory impressions. Thus females tend to be attracted to dampness and to soil level where, in grasses, host material is likely to be found. In such an area searching for hosts appears to be at random, but once an object that is a possible host is located there follows a careful examination and, if the object is “ considered ” a suitable host, oviposition follows. It appears that there are several definite criteria by which an object is accepted as a host suitable for oviposition. In general the hosts selected by the parasite are those which are suitable for the development of her progeny.
Das Geschlechter-Verhältnis vonPimpla turionellae (L.) (Hymenoptera: Ichneumonidae) — einem Parasiten vieler Lepidopteren-puppen — hängt von der Grösse des Wirtes ab, in welchem der Parasit sich entwickelt.
In einem kleinen Wirt, wieAnagasta kühniella (Zell.) (Pyralidae), entwickeln sich nur die Männchen. In einem mittelgrossen Wirt, wiePyrausta nubilalis (Hbn.),Galleria mellonella (L.)(Pyralidae), Pieris rapae (L.) (Pieridae), undTrichoplusia ni (Hbn.) (Noctuidae), entstehen Weibchen und Männchen in gleicher Zahl. In grossen Puppen vonAglais milberti
Latr.(Nymphalidae), Malacosoma americanum (F.) (Lasiocampidae) undDanaus plexippus
L.
(Danaidae) entwickeln sich mehr Weibchen. Im allgemeinen dauerte die Entwicklung in grösseren Puppen viellänger als in kleinen. Das
Gewicht des Parasiten nimmt zu mit dem Gewicht des Wirtes Die schwersten Männchen wiegen ungefähr neun mal mehr als die leichtesten.
Effect of superparasitism on sex ratio and mortality
- Kanungo K.
Studies in insect parasitism I–III. The effect of different hosts on the physiology, on the development and behaviour and on the sex‐ratio of Microbracon gelechiae Ashmead
- Narayanan E. S.
Host‐finding by insect parasites
- Laing J.
Nouvelle expérience permettant de disposer du sexe chez quelques Ichneumonidae Pimplinae
- Aubert J. F.
The Mymarid Caraphractus cinctus taken at Oxford in 1917
- Hamm A. H.
The effect of temperature on the sex ratio of parasitic Hymenoptera
- Moursi A. A.
Methoden zur Untersuchung von Wasserhymenopteren. Abderhalden E
- Rimsky-Korsakov
Competition among insect parasitoids
- Salt G.
Studies on the biology and ecology of Aphidius smithi Sharma & Subba Rao (Hymenoptera, Braconidae) a parasite of the pea aphid, Acyrthosiphon pisum (Harr.) (Homoptera, Aphididae)
- Wiackowski S. K.