Abstract: Plants are exposed to a suite of herbivorous attackers that often arrive sequentially. Herbivory affects interactions between the host plants and subsequently attacking herbivores. Moreover, plants may respond to herbivory by emitting volatile organic compounds (VOCs) that attract carnivorous natural enemies of the herbivores. However, information borne by VOCs is ubiquitous and may attract carnivores, such as parasitoids, that differ in their effectiveness at releasing the plant from its herbivorous attackers. Furthermore, the development of parasitoids within their herbivorous hosts, attacking a given host plant, may influence the elicitation of defensive reactions in the host plant. This may, in turn, affect the behavior of subsequent herbivores attacking the host plant. Here, we show that the species identity of a parasitoid had a more significant effect on defense responses of Brassica oleracea plants than the species identity of the herbivorous hosts of the parasitoids. Consequently, B. oleracea plants that were damaged by caterpillars (Pieris spp.) parasitized by different parasitoid species varied in the degree to which diamondback moths (Plutella xylostella) selected the plants for oviposition. Attracting parasitoids in general benefitted the plants by reducing diamondback moth colonization. However, the species of parasitoid that parasitized the herbivore significantly affected the magnitude of this benefit by its species-specific effect on herbivore–plant interactions mediated by caterpillar regurgitant. Our findings show that information-mediated indirect defense may lead to unpredictable consequences for plants when considering trait-mediated effects of parasitized caterpillars on the host plant and their consequences because of community-wide responses to induced plants.

Abstract: This study investigates complex effects of parasitoid infection on herbivore diet choice. Specifically, we examine how immunological resistance, parasitoid infection stage, and parasitoid taxonomic identity affect the pharmacophagous behavior of the polyphagous caterpillar, Grammia incorrupta (Arctiidae). Using a combination of lab and field experiments, we test the caterpillar’s pharmacophagous response to pyrrolizidine alkaloids (PAs) over the course of parasitoid infection, as well as the effect of dietary PAs on the caterpillar’s immunological response. Previous work from other systems gave the prediction that dietary PAs would be detrimental to the immune response and thus less acceptable to feeding early in the infection, when encapsulation of the parasitoid is most crucial. We found that the feeding acceptability of PAs was indeed low for caterpillars with early-stage parasitoid infections; however, this was not explained by PA interference with immune function. When allowed to choose among three host plant species, individuals harboring early-stage parasitoids increased their consumption of a nutritious plant containing antioxidants. This result was driven by wasp-parasitized caterpillars, whereas fly-parasitized caterpillars increased their consumption of plants containing iridoid glycosides. Individuals in the later time phase of infection exhibited an increase in PA intake that was consistent with previously reported self-medication behavior during late-stage parasitoid infection. This study reveals the depth of complexity and the dynamic nature of herbivore host plant choice, and underscores the importance of considering multitrophic interactions when studying insect diet choice.

Abstract: As a result of an intense host-parasite evolutionary arms race, parasitic wasps frequently display high levels of specialization on very few host species. For instance, in braconid wasps very few generalist species have been described. However, within this family, Cotesia sesamiae is a generalist species that is widespread in sub-Saharan Africa and develops on several lepidopteran hosts. In this study, we tested the hypothesis that C. sesamiae may be a cryptic specialist when examined at the intraspecific level. We sequenced exon 2 of CrV1, a gene of the symbiotic polyDNAvirus that is integrated into the wasp genome and is associated with host immune suppression. We found that CrV1 genotype was more closely associated with the host in which the parasitoid developed than any abiotic environmental factor tested. We also tested a correlation between CrV1 genotype and an infection with Wolbachia bacteria, which are known for their ability to induce reproductive isolation. The Wolbachia bacteria infection polymorphism was also found as a major factor explaining the genetic structure of CrV1, and, in addition, the best model explaining CrV1 genetic structure involved an interaction between Wolbachia infection and host species. We suggest that Wolbachia could act as an agent capable of maintaining advantageous alleles for host specialization in different populations of C. sesamiae. This mechanism could be applicable to other insect models because of the high prevalence of Wolbachia in insects.

Abstract: Optimality models of host-parasitoid relationships have traditionally assumed that host quality increases as a function of host size at parasitism However, trade-offs may play a crucial role in species evolution and should be found in host-parasitoid interactions where the host quality may differ between different sizes Here, we investigated the effects of host size differences of Monochamus alternatus larva on foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi Two-choice and non-choice experiments were conducted with M alternatus larvae to evaluate preference and performance of S harmandi, respectively Results from two-choice test showed that adult females prefer to attack large larvae rather than small larvae In no-choice tests, adult females needed more time to paralyze large larvae than small larvae before laying eggs on the body surface of M alternatus larvae and had lower survival and parasitism rate on those large larvae Foraging decisions of S harmandi led to the selection of the most profitable host size for parasitoid development, which showed more offspring gained on large M alternatus larvae than on small larvae and got higher body weight on those large hosts This study demonstrates the existence of trade-off occurring during host-parasitoids interactions according to host size related quality

Abstract: Bracoviruses are used by parasitoid wasps to allow development of their progeny within the body of lepidopteran hosts. In parasitoid wasps, the bracovirus exists as a provirus, integrated in a wasp chromosome. Viral replication occurs in wasp ovaries and leads to formation of particles containing dsDNA circles (segments) that are injected into the host body during wasp oviposition. We identified a large DNA transposon Maverick in a parasitoid wasp bracovirus. Closely related elements are present in parasitoid wasp genomes indicating that the element in CcBV corresponds to the insertion of an endogenous wasp Maverick in CcBV provirus. The presence of the Maverick in a bracovirus genome suggests the possibility of transposon transfers from parasitoids to lepidoptera via bracoviruses.

Abstract: Background: Resource partitioning is facilitated by adaptations along niche dimensions that range from morphology to behaviour. The exploitation of hidden resources may require specially adapted morphological or sensory tools for resource location and utilisation. Differences in tool diversity and complexity can determine not only how many species can utilize these hidden resources but also how they do so. Methodology and Principal Findings: The sclerotisation, gross morphology and ultrastructure of the ovipositors of a seven-member community of parasitic wasps comprising of gallers and parasitoids developing within the globular syconia (closed inflorescences) of Ficus racemosa (Moraceae) was investigated. These wasps also differ in their parasitism mode (external versus internal oviposition) and their timing of oviposition into the expanding syconium during its development. The number and diversity of sensilla, as well as ovipositor teeth, increased from internally ovipositing to externally ovipositing species and from gallers to parasitoids. The extent of sclerotisation of the ovipositor tip matched the force required to penetrate the syconium at the time of oviposition of each species. The internally ovipositing pollinator had only one type of sensillum and a single notch on the ovipositor tip. Externally ovipositing species had multiple sensilla types and teeth on their ovipositors. Chemosensilla were most concentrated at ovipositor tips while mechanoreceptors were more widely distributed, facilitating the precise location of hidden hosts in these wasps which lack larval host-seeking behaviour. Ovipositor traits of one parasitoid differed from those of its syntopic galler congeners and clustered with those of parasitoids within a different wasp subfamily. Thus ovipositor tools can show lability based on adaptive necessity, and are not constrained by phylogeny. Conclusions/Significance: Ovipositor structure mirrored the increasingly complex trophic ecology and requirements for host accessibility in this parasite community. Ovipositor structure could be a useful surrogate for predicting the biology of parasites in other communities.

Abstract: Dryocosmus kuriphilus (Hymenoptera: Cynipidae) is non-native to North America and induces formation of galls on petioles and leaves of all chestnut (Castanea spp., Fagales: Fagaceae). We investigated the interactions between the gall wasp D. kuriphilus, a native parasitoid, Ormyrus labotus (Hymenoptera: Ormyridae), and a non-native parasit- oid, Torymus sinensis (Hymenoptera: Torymidae). Galls were collected monthly from May to August and in January from four locations in the United States consisting of orchard-grown hybrid chestnuts (Hiram, OH and Meadowview, VA), suburban-grown orna- mental Chinese chestnuts (C. mollissima) (Broadview Heights, OH), or forest-grown American chestnuts (C. dentata) (Bowling Green, KY). Parasitoids were removed from galls and T. sinensis and O. labotus were identified using PCR-markers. The relative abundance of each parasitoid was compared in relation to collection date, habitat, presence of alternative hosts, and gall characteristics. T. sinensis was col- lected from each location and date, and was dominant in the orchard and suburban locations. However, relatively more O. labotus were collected within the forest, which had significant oak component and alternative cynipid hosts. O. labotus was only col- lected in spring and early summer, indicating the use of different summer and winter hosts. Observations suggest that in addition to parasitizing D. kuriphilus, O. labotus hyperparasitizes T. sinensis. T. sinensis has a longer ovipositor than O. labotus, and parasitized larger galls. This study improves our understanding of interactions between an invasive gall wasp, an intro- duced parasitoid, and native parasitoids, and illustrates novel relationships that may form as exotic species expand their geographic range.

Abstract: Parasites and parasitoids control behaviors of their hosts. However, the origin of the behavior evoked by the parasitic organism has been rarely identified. It is also not known whether the manipulation is universal or host-specific. Polysphinctine wasps, koinobiont ectoparasitoids of several spider species that manipulate host web-spinning activity for their own protection during pupation, provide an ideal system to reveal the origin of the evoked behavior. Larva of Zatypota percontatoria performed species-specific manipulation of theridiid spiders, Neottiura bimaculata and Theridion varians, shortly before pupation. Parasitized N. bimaculata produced a dense web, whereas parasitized T. varians built a cupola-like structure. The larva pupated inside of either the dense web or the cupola-like structure. We discovered that unparasitized N. bimaculata produce an analogous dense web around their eggsacs and for themselves during winter, while T. varians construct an analogous ‘cupola’ only for overwintering. We induced analogous manipulation in unparasitized hosts by altering ambient conditions. We discovered that the behavior evoked by larvae in two hosts was functionally similar. The larva evoked protective behaviors that occur in unparasitized hosts only during specific life-history periods.

Abstract: The performance of natural enemies, such as parasitoid wasps, is affected by differences in the quality of the host’s diet, frequently mediated by species or population-related differences in plant allelochemistry. Here, we compared survival, development time, and body mass in a generalist herbivore, the cabbage moth, Mamestra brassicae, and its solitary endoparasitoid, Microplitis mediator, when reared on two cultivated (CYR and STH) and three wild (KIM, OH, and WIN) populations of cabbage, Brassica oleracea. Plants either were undamaged or induced by feeding of larvae of the cabbage butterfly, Pieris rapae. Development and biomass of M. brassicae and Mi. mediator were similar on both cultivated and one wild cabbage population (KIM), intermediate on the OH population, and significantly lower on the WIN population. Moreover, development was prolonged and biomass was reduced on herbivore-induced plants. However, only the survival of parasitized hosts (and not that of healthy larvae) was affected by induction. Analysis of glucosinolates in leaves of the cabbages revealed higher levels in the wild populations than cultivars, with the highest concentrations in WIN plants. Multivariate statistics revealed a negative correlation between insect performance and total levels of glucosinolates (GS) and levels of 3-butenyl GS. However, GS chemistry could not explain the reduced performance on induced plants since only indole GS concentrations increased in response to herbivory, which did not affect insect performance based on multivariate statistics. This result suggests that, in addition to aliphatic GS, other non-GS chemicals are responsible for the decline in insect performance, and that these chemicals affect the parasitoid more strongly than the host. Remarkably, when developing on WIN plants, the survival of Mi. mediator to adult eclosion was much higher than in its host, M. brassicae. This may be due to the fact that hosts parasitized by Mi. mediator pass through fewer instars, and host growth is arrested when they are only a fraction of the size of healthy caterpillars. Certain aspects of the biology and life-history of the host and parasitoid may determine their response to chemical challenges imposed by the food plant.

Abstract: In attempting to explain the marked interspecific variation evident in many components of life-history in parasitoid wasps, biologists have sought to identify general predictors of suites of ‘important’ life-history traits. Two predictors currently in general use are: (1) the parasitoid mode of larval development in relation to future host growth and development [no further host growth and development (= idiobiosis) versus continued host growth and development (= koinobiosis)]; and (2) the ovigeny index (the degree to which the lifetime potential complement of eggs is mature at the start of adult life in females). These have been postulated to share several life-history correlates, and an earlier comparative analysis showed the predictors to be associated. Two questions are thus posed: which life-history variables are actually common to both idio/koinobiosis and the ovigeny index, and which are responsible for the link between these two axes of life-history diversity? Through comparative analyses of a database of life-history traits for 133 parasitoid wasp species, four life-history correlates out of the 11 we investigated are shown to account for the association between the two predictors: the relative level of resource investment per egg (degree of yolk richness, which is lower in koinobionts), pre-adult lifespan (longer in koinobionts), female lifespan (shorter in koinobionts), and maximum egg load (larger in koinobionts). Our findings pave the way for full integration of the dichotomous hypothesis with the ovigeny index hypothesis, to provide a holistic perspective on parasitoid wasp life-history diversity and evolution.

Abstract: 1. The bottom-up factors that determine parasitoid host use are an important area of research in insect ecology. Host size is likely to be a primary cue for foraging parasitoids due to its potential influence on offspring development time, the risk of multiparasitism, and host immunocompetence. Host size is mediated in part by host-plant traits that influence herbivore growth and potentially affect a herbivore's quality as a host for parasitoids. 2. Here, we tested how caterpillar host size and host plant species influence adult fly parasitoid size and whether host size influences wasp parasitoid sex allocation. We measured the hind tibia lengths and determined the sex of wasp and fly parasitoids reared from 11 common host species of polyphagous caterpillars (Limacodidae) that were in turn reared on foliage of seven different host plant species. 3. We also tested how host caterpillar species, host caterpillar size, and host and parasitoid phenology affect how the parasitoid community partitions host resources. We found evidence that parasitoids primarily partition their shared hosts based on size, but not by host species or phenology. One index of specialisation (d′) supports our observation that these parasitoids are quite generalised within the Limacodidae. In general, wasps were reared from caterpillars collected in early instars, while flies were reared from caterpillars collected in late instars. Furthermore, for at least one species of solitary wasp, host size influenced sex allocation of offspring by ovipositing females. 4. Host-plant quality indirectly affected the size attained by a tachinid fly parasitoid through its direct effects on the size and performance of the caterpillar host. The host plants that resulted in the highest caterpillar host performance in the absence of enemies also yielded the largest parasitoid flies, which suggests that host plant quality can cascade up to influence the third trophic level.

Abstract: The response of the generalist egg parasitoid Ooencyrtustelenomicida (Vassiliev) (Hymenoptera: Encyrtidae) to host-related chemical cues from tomato plants, Solanum lycopersicum L., and adults of Nezara viridula (L.) (Heteroptera: Pentatomidae) was investigated in laboratory-based no-choice and paired-choice tests. In Y-tube olfactometer experiments, when female wasps were exposed to volatiles from plants in different conditions, they were attracted only to volatiles produced by N. viridula adult-infested tomato plants. When female wasps were exposed to adults of N. viridula, they were attracted to volatiles from virgin males, and, at a lower level, to volatiles from mated females in preoviposition state. Finally, studies in open arena showed that chemical footprints left by adults of N. viridula did not induce arrestment responses in wasp females. These results are discussed in terms of extrinsic competition with other beneficial egg parasitoids that in field can compete for the same egg mass, since intraguild interactions may affect the success of a biological control program.

Abstract: Communities are riddled with indirect species interactions and these interactions can be modified by organisms that are parasitic or symbiotic with one of the indirectly interacting species. By inducing plant responses, herbivores are well known to alter the plant quality for subsequent feeders. The reduced performance of herbivores on induced plants cascades into effects on the performance of higher trophic level organisms such as parasitoids that develop inside herbivores. Parasitoids themselves may also, indirectly, interact with the host plant by affecting the behaviour and physiology of their herbivorous host. Here, we show that, through their herbivorous host, larvae of two parasitoid species differentially affect plant phenotypes leading to asymmetric interactions among parasitoid larvae developing in different hosts that feed on the same plant. Our results show that temporally separated parasitoid larvae are involved in indirect plant-mediated interactions by a network of trophic and non-trophic relationships.

Abstract: Current knowledge about polysphinctine parasite wasps' interactions with their spider hosts is very fragmented and incomplete. This study presents the host specificity of Zatypota percontatoria (Muller) (Hymenoptera: Ichneumonidae) and its adaptation to varying host availability. Two years of field observations show that Z. percontatoria is a stenophagous parasitoid that parasitizes only five closely related web-building spiders of the family Theridiidae (Araneae). Within the Theridiidae it attacks only species belonging to a small group of species, here called the “Theridion” group. These hosts have a similar biology, but are available at different levels of abundance and at different sizes over the season. Laboratory experiments showed that this wasp species ignores linyphiid, araneid or dictynid spiders and accepts only theridiid spiders of the “Theridion” group. In the field study, wasp females preferred older juvenile and sub-adult female spider instars with intermediate body size. Only 5% of the parasitized spiders were males. Parasitism in the natural population of theridiid spiders was on average 1.3%. Parasitism was most frequent on two species, Theridion varians Hahn in 2007 and Neottiura bimaculata Linnaeus in 2008. The parasitization rate was positively correlated with spider abundance. The wasp responded adaptively to seasonal changes in host abundance and host body size and shifted host preference according to the availability of suitable hosts during, as well as between, seasons. In spring and summer the highest percentage of parasitism was on T. varians and in autumn it was on N. bimaculata.

Abstract: Plant infestation, stem borer density, parasitism, and parasitoid abundance were assessed during two years in two host plants, Zea mays (L.) (Cyperales: Poaceae) and Sorghum bicolor (L.) (Cyperales: Poaceae), in cultivated habitats. The four major host plants (Cyperus spp., Panicum spp., Pennisetum spp., and Sorghum spp.) found in natural habitats were also assessed, and both the cultivated and natural habitat species occurred in four agroecological zones in Kenya. Across habitats, plant infestation (23.2%), stem borer density (2.2 per plant), and larval parasitism (15.0%) were highest in maize in cultivated habitats. Pupal parasitism was not higher than 4.7% in both habitats, and did not vary with locality during each season or with host plant between each season. Cotesia sesamiae (Cameron) and C. flavipes Cameron (Hymenoptera: Braconidae) were the key parasitoids in cultivated habitats (both species accounted for 76.4% of parasitized stem borers in cereal crops), but not in natural habitats (the two Cotesia species accounted for 14.5% of parasitized stem borers in wild host plants). No single parasitoid species exerted high parasitism rates on stem borer populations in wild host plants. Low stem borer densities across seasons in natural habitats indicate that cereal stem borer pests do not necessarily survive the non-cropping season feeding actively in wild host plants. Although natural habitats provided refuges for some parasitoid species, stem borer parasitism was generally low in wild host plants. Overall, because parasitoids contribute little in reducing cereal stem borer pest populations in cultivated habitats, there is need to further enhance their effectiveness in the field to regulate these pests.

Abstract: The parasitic wasp Ixodiphagus hookeri parasitizes hard ticks and is therefore considered as a potential candidate for biological control of ticks. However, there are still considerable gaps of knowledge about the biology of I. hookeri, especially for European populations. Thus, the present study was performed to assess important life-history parameters of the parasitoid in Germany. Field studies accomplished in three successive years revealed that unfed Ixodes ricinus nymphs are infested by the parasitoid at a low but constant rate of 1.9―3.8% and that adult wasps are present only during a short period in late summer. The mean developmental time of wasps in I. ricinus nymphs ranged from 28 to 70 days under constant laboratory conditions and was prolonged in the second half of the year. Bioassays on parasitization and host preference behaviour showed that unfed nymphs of the host species I. ricinus are significantly preferred in experiments, in which unfed and engorged larvae as well as fully engorged nymphs were offered as alternatives. The marsh tick Dermacentor reticulatus was not accepted as an alternative host. Our data show that the investigated I. hookeri populations differ markedly from populations in other regions of the world in many aspects. The adaptation of different strains to local conditions explains the limited success of imported strains in earlier biological control attempts and highlights the importance of doing research to enhance the control potential of native strains.

Abstract: Diachasmimorpha kraussii is a larval parasitoid of dacine fruit flies. Host utilisation behaviour, including field foraging behaviour, is poorly known in this species. The diurnal foraging behaviour of D. kraussii and one of its common hosts, Bactrocera tryoni, in a nectarine orchard was concurrently recorded. Observations of mating, resting, feeding and oviposition were taken two-hourly on 42 trees, commencing at 07:00 h and terminating at 17:30 h, for 17 days. Resting and oviposition were common events within the orchard for both species, while mating behaviours were not recorded in the orchard for either species. Feeding was not observed for D. kraussii and was rare for B. tryoni. At the level of the individual tree there was a very weak, but significant correlation between parasitoid and fly abundance over a day, but when broken down to the individual observation periods the correlations were absent, or were weakly significant in an inconsistent manner (i.e. sometimes positively correlated, sometimes negatively correlated). At the orchard level, abundance of the parasitoid was not correlated with adult fly abundance. Results suggest that D. kraussii forage independently to adult B. tryoni, a result consistent with a prediction that their foraging is largely driven by larval or plant damage cues.

Abstract: Parasitoid disturbance populations in agroecosystems can be maintained through the provision of habitat refuges with host resources. However, specialized herbivores that feed on different host plants have been shown to form host-specialized races. Parasitoids may subsequently specialize on these herbivore host races and therefore prefer parasitizing insects from the refuge, avoiding foraging on the crop. Evidence is therefore required that parasitoids are able to move between the refuge and the crop and that the refuge is a source of parasitoids, without being an important source of herbivore pests. A North-South transect trough the Chilean Central Valley was sampled, including apple orchards and surrounding Pyracantha coccinea (M. Roem) (Rosales: Rosacea) hedges that were host of Eriosoma lanigerum (Hemiptera: Aphididae), a globally important aphid pest of cultivated apples. At each orchard, aphid colonies were collected and taken back to the laboratory to sample the emerging hymenopteran parasitoid Aphelinus mali (Hymenoptera: Aphelinidae). Aphid and parasitoid individuals were genotyped using species-specific microsatellite loci and genetic variability was assessed. By studying genetic variation, natural geographic barriers of the aphid pest became evident and some evidence for incipient host-plant specialization was found. However, this had no effect on the population-genetic features of its most important parasitoid. In conclusion, the lack of genetic differentiation among the parasitoids suggests the existence of a single large and panmictic population, which could parasite aphids on apple orchards and on P. coccinea hedges. The latter could thus comprise a suitable and putative refuge for parasitoids, which could be used to increase the effectiveness of biological control. Moreover, the strong geographical differentiation of the aphid suggests local reinfestations occur mainly from other apple orchards with only low reinfestation from P. cocinnea hedges. Finally, we propose that the putative refuge could act as a source of parasitoids without being a major source of aphids.

Abstract: Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae, Aphidiinae) is a parasitic wasp which plays an important role in the biological control of a number of aphid species. Through assessment of its thermal biology and low temperature tolerance, this study ascertains the establishment potential of L. testaceipes in cool temperate climates typical of northern Europe. The developmental threshold of L. testaceipes was 5.8°C. Rearing of parasitoids at shorter day lengths and lower temperatures indicated no ability to enter a diapause state. The supercooling points (SCP) of non-acclimated and acclimated parasitoid life stages were between −24.6°C and −17.7°C, with LTemp50 temperatures approaching these values, indicating a high level of cold tolerance in short exposures. At 5°C the LTime50 of acclimated larvae within parasitized aphids was 42.8 days. Acclimated pupae continued to develop with 54% adult emergence from mummies within 60 days. Acclimated parasitoid larvae and pupae, within living and mummified aphids, continued to develop during 70 days of winter field exposure and emerging adult parasitoids were reproductively viable under field conditions. These data indicate that where suitable host species are available throughout the year, L. testaceipes would be able to establish in northern Europe.

Abstract: Many parasitoid species have preference for certain stages of hosts to parasitize but the underlying behavioral mechanisms of such preference are still poorly understood, making it difficult to evaluate host-parasitoid interactions and their effects on the success of biological control programs. Here, we report our work on a parasitoid Aphidius ervi Haliday on the pea aphid Acyrthosiphon pisum (Harris). We show that with the increase of host age, female parasitoids are more likely to encounter and to attack their hosts but the hosts develop increasingly greater defensive capabilities. Encounter almost always triggers attack attempt; however, increasing attack attempts do not proportionally lead to ovipositor probings and increasing ovipositor probings do not proportionally translate into ovipositions. These asymmetric responses may be interpreted as that A. ervi females prefer to parasitize older aphids for higher fitness return but those aphids can better defend themselves, and as a consequence, A. ervi females may achieve the highest gain by attacking aphids of intermediate ages. We suggest that A. ervi females forage in a manner consistent with the optimal foraging theory, trading off host handling time with fitness returns.

Abstract: Behavioral tactics play a crucial role in the evolution of species and are likely to be found in host-parasitoid interactions where host quality may differ between host developmental stages. We investigated foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi in relation to two distinct host developmental stages: larvae and pupae. Two colonies of parasitoids were reared on larvae of Monochamus alternatus and Saperda populnea (Cerambycidae: Lamiinae). Paired-choice and non-choice experiments were used to evaluate the preference and performance of S. harmandi on larvae and pupae of the two species. Foraging decisions and offspring fitness-related consequences of S. harmandi led to the selection of the most profitable host stage for parasitoid development. Adult females from the two colonies oviposited more quickly on pupae as compared to larvae of M. alternatus. Subsequently, their offspring development time was faster and they gained higher body weight on the pupal hosts. This study demonstrates optimal foraging of intraspecific detente that can occur during host-parasitoid interactions, of which the quality of the parasitism (highest fitness benefit and profitability) is related to the host developmental stage utilized. We conclude that S. harmandi is able to perfectly discriminate among host species or stages in a manner that maximizes its offspring fitness. The results indicated that foraging potential of adults may not be driven by its maternal effects, also induced flexibly with encountering prior host quality.

Abstract: Investigating complex parasitic life cycles is important for understanding the major fitness components that drive the evolution of host-parasite systems. The rare condition of heterotrophic heteronomy, in which the sexes utilize disparate host taxa, is a poorly understood complex parasitic lifestyle. One of only two known examples occurs in the Myrmecolacidae, an unusual family of the parasitoid order Strepsiptera (Insecta), in which males parasitize ants while females parasitize grasshoppers, crickets, and praying mantids. Here, we reconstruct the evolutionary pattern and timescale of host-use in a set of morphologically cryptic myrmecolacid taxa currently identified as Caenocholax fenyesi. We find that (i) C. fenyesi contains at least ten cryptic lineages consistent with separate species; (ii) Fossil evidence suggests a very low molecular clock rate and an ancient origin for cryptic lineages; (iii) Diversity among Caenocholax species is partitioned by geography and host association of the female; and (iv) Switches in host usage are uncoupled between the sexes, with changes in female host preference accompanying diversification. This study represents the first phylogeographical analysis of any strepsipteran, and the first molecular examination of host-use for a heterotrophic heteronomous taxon. Our results have implications for the understanding of evolution, host usage and estimated species richness in parasitic taxa.