Superparasitism evolution: adaptation or manipulation?

Superparasitism refers to the oviposition behavior of parasitoid females who lay their eggs in an already parasitized host. This often yields intense competition among larvae that are sharing the same host. Why would a female oviposit in such hostile habitat instead of looking for a better quality, unparasitized host? Here we present a continuous-time model of host-parasitoid interaction and discuss alternative scenarios. This model is first used to analyze the evolution of the superparasitism behavior of a solitary proovigenic parasitoid under both time and egg limitation. Then, following the recent discovery by Varaldi et al., we allow the parasitoid to be infected by a virus that alters the superparasitism behavior of its host to enhance its own horizontal transmission. The analysis of the coevolution of this manipulative behavior with the oviposition behavior of uninfected females clarifies and quantifies the conflict that emerges between the parasitoid and its virus. The model also yields new testable predictions. For example, we expect that uninfected parasitoids should superparasite less after coevolving with the manipulative virus. More generally, this model provides a theoretical framework for analyzing the evolution of the manipulation of parasitoid life-history traits by microparasites.     

Effect of adult feeding and timing of host exposure on the fertility and longevity of the parasitoid Anaphes flavipes

The parasitoid Anaphes flavipes (Foerster) (Hymenoptera: Mymaridae) is a gregarious egg parasitoid which is widely used in biological control against important crop pest beetles of the genus Oulema (Coleoptera: Chrysomelidae). Here, we present the first experimental examination of the influence of adult feeding and timing of host exposure on the longevity and fertility of this parasitoid. We confirmed a positive effect of adult feeding on longevity of both sexes. Fed parasitoids lived 3× longer than unfed ones. On the other hand, adult feeding and feeding time had no effect on female fertility. The number of hatched offspring was not increased by adult feeding, which suggests that the parasitoid emerges with already mature ovaries (proovigenic type). However, the fertility of fed females was strongly influenced by the timing of host egg exposure. By providing distinct groups of parasitoids with host eggs at different times, we were able to show lower fertility of fed females that had been offered host eggs more than 24 h after hatching. Our results thus show that the parasitoid's fertility is determined by her age at the time of parasitization rather than by feeding.     

Competitive outcome of multiple infections in a behavior‐manipulating virus/wasp interaction

Infections by multiple parasites are common in nature and may impact the evolution of host–parasite interactions. We investigated the existence of multiple infections involving the DNA virus LbFV and the Drosophila parasitoid Leptopilina boulardi. This vertically transmitted virus forces infected females to lay their eggs in already parasitized Drosophila larvae (a behavior called superparasitism), thus favoring its spread through horizontal transmission. Previous theoretical work indicated that the evolution of the level of the manipulation strongly depends on whether infected parasitoids can be re‐infected or not. Here, we describe a strain of LbFV that differs from the reference strain by showing a deletion within the locus used for PCR detection. We used this polymorphism to test for the existence of multiple infections in this system. Viral strains did not differ on their vertical or horizontal transmission rates nor on the way they affect the parasitoid''s phenotype, including their ability to manipulate behavior. Although already infected parasitoids were much less susceptible to new infection than uninfected ones, frequent coinfection was detected. However, following coinfection, competition between viral strains led to the rapid elimination of one strain or the other after a few generations of vertical transmission. We discuss the implications of these results for the evolution of the behavioral manipulation.     

Prevalence of a virus inducing behavioural manipulation near species range border

The densities of conspecific individuals may vary through space, especially at the edge of species range. This variation in density is predicted to influence the diffusion of species‐specific horizontally transmitted symbionts. However, to date there is very little data on how parasite prevalence varies around the border of a host species. Using a molecular epidemiology approach, we studied the prevalence of a vertically and horizontally transmitted virus at the edge of the geographic range of its insect host, the Drosophila parasitoid wasp Leptopilina boulardi. L. boulardi is a Mediterranean parasitoid species showing a recent range expansion to the north (in France). The LbFV virus manipulates the behaviour of females, increasing their tendency to lay additional eggs in already parasitized Drosophila larvae (superparasitism). This is beneficial for the virus because it allows the virus to be horizontally transferred during superparasitism. We show that LbFV prevalence is very high in central populations, intermediate in marginal populations and almost absent from newly established peripheral populations of L. boulardi. We failed to detect any influence of temperature and diapause on viral transmission efficiency but we observed a clear relationship between prevalence and parasitoid density, and between parasitoid density and the occurrence of superparasitism, as predicted by our epidemiological model. Viral strains were all efficient at inducing the behavioural manipulation and viral gene sequencing revealed very low sequence variation. We conclude that the prevalence reached by the virus critically depends on density‐dependent factors, i.e. superparasitism, underlying the selective pressures acting on the virus to manipulate the behaviour of the parasitoid.     

Response of parasitoid egg load to host dynamics and implications for egg load evolution

A theoretical debate about whether parasitoids should be time or egg limited now recognizes both as feasible, and interest has turned to determining the circumstances under which each might arise in the field, and their implications for parasitoid behaviour and evolution. Egg loads of parasitoids sampled from the field are predicted to show a negative response to host availability, but empirical support for this relationship is scarce. We measured how a parasitoid's egg load responded to seasonal fluctuations in host population density and recorded the predicted correlation. In early summer, parasitoids were at high risk of time limitation due to low host availability, and in late summer, their offspring were at greater risk of egg limitation due to high host availability. Despite clear seasonal changes in selection pressures on egg load and lifespan, the parasitoid showed no evidence of seasonal variation in its reproductive strategy. We made minor modifications to a previously published model to explore the effects of seasonal variation in host availability on optimal investments in eggs and lifespan and obtained several new results. In particular, under circumstances analogous to some of those observed in our field study, temporal stochasticity in reproductive opportunities can cause investments in eggs to increase, rather than decrease as previously predicted. Our model results helped to explain the parasitoid's lack of a seasonally varying reproductive strategy. Understanding the evolution of parasitoid egg load would benefit from a shift of research emphasis from purely stochastic variation in parasitoid reproductive opportunities to greater consideration of host dynamics.     

Molecular Detection, Penetrance, and Transmission of an Inherited Virus Responsible for Behavioral Manipulation of an Insect Parasitoid

For insects, the prevalence of numerous vertically transmitted viruses can be high in their host populations. These viruses often have few, if any, pathological effects on their hosts, and consequently, many of them can remain unnoticed for long periods, despite their potential role in the evolution of the host phenotype. Some females of Leptopilina boulardi, a solitary parasitoid of Drosophila larvae, are infected by an inherited virus (LbFV) that manipulates the behavior of the wasp by increasing its tendency to lay eggs in a host that is already parasitized (superparasitism). This behavioral alteration allows horizontal transmission of the virus within superparasitized Drosophila larvae. Using suppressive subtractive hybridization with infected and uninfected lines, we identified one putative viral sequence. Based on this sequence, we developed a simple PCR test. We tested the correlation between the superparasitism phenotype and PCR amplification of the putative viral marker using several experimental conditions (including horizontal transfers) and several parasitoid genotypes. All of the results revealed that there was a perfect match between the superparasitism phenotype and the amplification profile, which validated use of the molecular marker as a tool to track the presence of the virus and provided the first genomic data for this fascinating virus. The results also show that there was very efficient horizontal and vertical transmission of LbFV, which probably explains its high prevalence in the French populations that we sampled (67 and 70% of infected females). This manipulative virus is likely to play a major role in the ecology and evolution of its parasitoid host.     

Egg load dynamics and the risk of egg and time limitation experienced by an aphid parasitoid in the field

Insect parasitoids and herbivores must balance the risk of egg limitation and time limitation in order to maximize reproductive success. Egg and time limitation are mediated by oviposition and egg maturation rates as well as by starvation risk and other determinants of adult lifespan. Here, we assessed egg load and nutritional state in the soybean aphid parasitoid Binodoxys communis under field conditions to estimate its risk of becoming either egg‐ or time‐limited. The majority of female B. communis showed no signs of egg limitation. Experimental field manipulations of B. communis females suggested that an average of 4–8 eggs were matured per hour over the course of a day. Regardless, egg loads remained constant over the course of the day at approximately 80 eggs, suggesting that egg maturation compensates for oviposition. This is the first case of such “egg load buffering” documented for a parasitoid in the field. Despite this buffering, egg loads dropped slightly with increasing host (aphid) density. This suggests that egg limitation could occur at very high host densities as experienced in outbreak years in some locations in the Midwestern USA. Biochemical analyses of sugar profiles showed that parasitoids fed upon sugar in the field at a remarkably high rate. Time limitation through starvation thus seems to be very low and aphid honeydew is most likely a source of dietary sugar for these parasitoids. This latter supposition is supported by the fact that body sugar levels increase with host (aphid) density. Together, these results suggest that fecundity of B. communis benefits from both dynamic egg maturation strategies and sugar‐feeding.     

Host feeding in insect parasitoids: why destructively feed upon a host that excretes an alternative?

Host feeding is the consumption of host tissue by the adult female parasitoid. We studied the function of destructive host feeding and its advantage over non‐destructive feeding on host‐derived honeydew in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We allowed parasitoids to oviposit until they attempted to host feed. We either prevented or allowed host feeding. Parasitoids had access to sucrose solution, with or without additional access to honeydew. Parasitoids that were allowed to host feed did not have a higher egg load 20 or 48 h after host feeding than parasitoids prevented from host feeding. Host feeding did not increase the number of eggs matured within these periods, nor did the time spent host feeding positively affect any of these response variables. On the other hand, the presence of honeydew did have a positive effect on egg load 20 and 48 h after host feeding compared with parasitoids deprived of honeydew. Parasitoids with access to honeydew matured more eggs within these periods than honeydew‐deprived parasitoids. Host feeding increased life expectancy, but this effect was nullified when honeydew was supplied after the host‐feeding attempt. In conclusion, feeding on honeydew could be an advantageous alternative to host feeding in terms of egg quantity and longevity. This applies especially to parasitoids exploiting Homoptera, because these parasitoids can obtain honeydew from the host itself. It is possible that destructive host feeding has evolved to enable females to sustain the production of high‐quality anhydropic eggs, which may be important in the parasitoid's natural environment. We argue that future studies should take natural alternative food sources into more consideration.     

Reproduction now or later: optimal host-handling strategies in the whitefly parasitoid Encarsia formosa

We developed a dynamic state variable model for studying optimal host‐handling strategies in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We assumed that (a) the function of host feeding is to gain nutrients that can be matured into eggs, (b) oögenesis is continuous and egg load dependent, (c) parasitoid survival is exponentially distributed and (d) parasitoids encounter hosts randomly, are autogenous and have unlimited access to non‐host food sources to obtain energy for maintenance and activity. The most important prediction of the model is that host feeding is maladaptive under field conditions of low host density (0.015 cm^?2) and short parasitoid life expectancy (maximum reproductive period of 7 d). Nutrients from the immature stage that can be matured into eggs are sufficient to prevent egg limitation. Both host density and parasitoid life expectancy have a positive effect on the optimal host‐feeding ratio. Parasitoids that make random decisions gain on average only 35% (0.015 hosts cm^?2) to 60% (1.5 hosts cm^?2) of the lifetime reproductive success of parasitoids that make optimal decisions, independent of their life expectancy. Parameters that have a large impact on lifetime reproductive success and therefore drive natural selection are parasitoid life expectancy and the survival probability of deposited eggs (independent of host density), the number of host encounters per day (when host density is low) and the egg maturation rate and number of host types (when host density is high). Explaining the evolution of host‐feeding behaviour under field conditions requires field data showing that life expectancy in the field is not as short as we assumed, or may require incorporation of variation in host density. Incorporating variation in walking speed, parasitised host types or egg resorption is not expected to provide an explanation for the evolution of host‐feeding behaviour under field conditions.     

Choosy egg parasitoids: Specificity of oviposition-induced pine volatiles exploited by an egg parasitoid of pine sawflies

Generalist parasitoids are well‐known to be able to cope with the high genotypic and phenotypic plasticity of plant volatiles by learning odours during their host encounters. In contrast, specialised parasitoids often respond innately to host‐specific cues. Previous studies have shown that females of the specialised egg parasitoid Chrysonotomyia ruforum Krausse (Hymenoptera: Eulophidae) are attracted to volatiles from Pinus sylvestris L. induced by the egg deposition of its host Diprion pini L. (Hymenoptera: Diprionidae), when they have previously experienced pine twigs with host eggs. In this study we investigated by olfactometer bioassays how specifically C. ruforum responded to oviposition‐induced plant volatiles. Furthermore, we studied whether parasitoids show an innate response to oviposition‐induced pine volatiles. Naïve parasitoids were not attracted to oviposition‐induced pine volatiles. The attractiveness of volatiles from pines carrying eggs was shown to be specific for the pine and herbivore species, respectively (species specificity). We also tested whether not only oviposition, but also larval feeding, induces attractive volatiles (developmental stage specificity). The feeding of D. pini larvae did not induce the emission of P. sylvestris volatiles attractive to the egg parasitoid. Our results show that a specialist egg parasitoid does not innately show a positive response to oviposition‐induced plant volatiles, but needs to learn them. Furthermore, the results show that C. ruforum as a specialist does not learn a wide range of volatiles as some generalists do, but instead learns only a very specific oviposition‐induced plant volatile pattern, i.e., a pattern induced by the most preferred host species laying eggs on the most preferred food plant.     

Modifications of Trichogramma Behaviors During the Exploitation of Host Patches Induced by the Insecticide Chlorpyrifos

Parasitoid species are key species because they regulate numerous insect species, including pests. An efficient infestation of hosts is critical to the development of parasitoid populations. In this article, we investigate the effects of the widely used insecticide chlorpyrifos on the exploitation of a patch of host by a parasitoid, Trichogramma brassicae. We show that chlorpyrifos increased the efficiency of parasitoid females in the infestation of the first host egg by decreasing its super-parasitization. Except for the first egg, all infested eggs were infested only once by both control and treated females; therefore, the insecticide did not impede the detection of a host that had already been infested. We did find that the insecticide affected the mode of rejection of infested eggs. At the beginning of the exploitation of the patch, females exposed to the insecticide made more antennal rejections than controls but eventually made more ovipositor rejections. These results suggest that the insecticide initially stimulated the antennal perception of the infested host but finally led to the saturation of this perception. Parasitoids compensated for this loss of antennal perception via ovipositor perception of infested eggs. This switch of behavior corresponds to a decrease in efficiency, as it is much more time consuming; therefore, females exposed to the insecticide had to stay longer on the patch for an equal rate of exploitation relative to controls. The infestation of host eggs is a crucial behavior for parasitoids, enabling their reproduction and the development of their species. By decreasing the antennal recognition of infested eggs, chlorpyrifos continues to be detrimental even when parasitoids survive exposure.     

Role of volatile semiochemicals in host location by the egg parasitoid Anagrus breviphragma

Recent investigations conducted on several tritrophic systems have demonstrated that egg parasitoids, when searching for host eggs, may exploit plant synomones that have been induced as a consequence of host oviposition. In this article we show that, in a system characterized by host eggs embedded in the plant tissue, naïve females of the egg parasitoid Anagrus breviphragma Soyka (Hymenoptera: Mymaridae) responded in a Y‐tube olfactometer to volatiles from leaves of Carex riparia Curtis (Cyperaceae) containing eggs of one of its hosts, Cicadella viridis (L.) (Hemiptera: Cicadellidae). The wasp did not respond to host eggs or to clean leaves from non‐infested plants compared with clean air, whereas it showed a strong preference for the olfactometer arm containing volatiles of leaves with embedded host eggs, compared with the arm containing volatiles of leaves from a non‐infested plant or host eggs extracted from the plant. When the eggs were removed from an infested leaf, the parasitoid preference was observed only if eggs were added aside, suggesting a synergistic effect of a local plant synomone and an egg kairomone. The parasitoid also responded to clean leaves from an egg‐infested plant when compared with leaves from a non‐infested plant, indicating a systemic effect of volatile induction.     

Egg load of lab-cultured <Emphasis Type="Italic">Anaphes iole</Emphasis> and effects of mate presence and exposure time on load depletion

Anaphes iole Girault (Hymenoptera: Mymaridae) is a solitary egg parasitoid of Lygus bugs (Heteroptera: Miridae) in North America. This research considered factors that might impact the egg load of lab-cultured A .iole females, reared from Lygus hesperus Knight egg patches. The following hypotheses were tested: (1) egg load was related to body size and not affected by female age, and (2) egg load depletion was not affected by mate presence and time (in days) that females were exposed to host patches. Initial egg load averaged 48 mature eggs and no immature eggs were detected in the ovarioles of dissected females. Egg load was neither related to body size (hind tibia or forewing length) nor affected significantly by age (0, 1 or 2days old honey-fed females). Mate presence (females with or without males) and exposure time (1, 3 or 5days on the same host patch) had no effect on egg load depletion. Females usually depleted most of their egg load within 24h. From 86 to 92% of females contained less than six mature eggs and no immature eggs after 1, 3 or 5days of exposure to host patches. The results of this study suggest that A. iole females are certainly pro-ovigenic and initial egg load does not correlate with body size or age. Since mated and unmated females deplete most of their egg load in 24h, time-efficient production of progeny may result when ovipositing parasitoids are exposed to suitable hosts for just a few days.The United States Government has the right to retain a non-exclusive, royalty-free license in and to any copyright of this article. This article reports the results of research only. Mention of a commercial or proprietary product does not constitute an endorsement of the product by the United States Department of Agriculture.     

Effect of host deprivation on egg quality,egg load,and oviposition in a solitary parasitoid,Chetogena edwardsii (Diptera: Tachinidae)

Solitary parasitoids are limited to laying one egg per host because larvae compete within hosts. If host encounter rate is low, females should not increase the number of eggs/host in response. The tachinid fly, Chetogena edwardsii,was used to evaluate the effect of host deprivation on egg accumulation, oviposition behavior, and egg quality in a solitary parasitoid. Females deprived of hosts for 2– 7 days accumulate about 1 day's supply of eggs. Egg output of deprived females once hosts are restored does not differ from that of control females. Deprived females retain one egg in the uterus where it undergoes embryogenesis. Maggots emerging from retained eggs are more likely to survive in hosts molting in 40 h or less after receipt of an egg than are maggots emerging from eggs fertilized shortly before oviposition. Egg retention is a consequence of host deprivation that permits females to broaden the range of hosts they can exploit to include soon-to-molt hosts and possibly multiply parasitized hosts.     

Effect of entomopoxvirus infection of Pseudaletia separata larvae on the oviposition behavior of Cotesia kariyai

Parasitoid behavior and oviposition were monitored to investigate the ability of Cotesia kariyai (Watanabe) (Hymenoptera: Braconidae) to distinguish between entomopoxvirus-infected and noninfected larvae of Pseudaletia separata Walker (Lepidoptera: Noctuidae). Comparison of individual means revealed that searching time was not significantly different between treatments. Ovipositional time, however, differed significantly after day 8 post virus inoculation. The parasitoid adopted ovipositional posture on infected and noninfected host irrespective of the stage of infection and did not distinguish infected from noninfected larvae up to 4 days post infection. Mean number of larvae stung by the parasitoid was not influenced by the length of time interval between exposure to the virus. However, duration of ovipositor insertion was influenced by the time interval between exposure to the virus and subsequent exposure to parasitoid females. Female parasitoids did not completely reject infected larvae as unsuitable for egg deposition. However, 5 days after virus inoculation they rejected significantly more infected than noninfected larvae. Furthermore, significantly more eggs were laid in noninfected than infected larvae from day 5 following virus administration. These observations suggest that probing by Cotesia kariyai may provide information concerning host suitability.     

Are Lab-cultured <Emphasis Type="Italic">Anaphes iole</Emphasis> Females Strictly Proovigenic?

Anaphes iole Girault (Hymenoptera: Mymaridae) is a solitary egg parasitoid of Lygus bugs (Heteroptera: Miridae) in North America. Circumstantial evidence suggests that A. iole females are strictly proovigenic. This study was designed to determine if honey-fed A. iole females could in fact mature additional eggs if exposed to hosts for a few days then removed from hosts and held at 25 °C for 0, 3, or 6 days. Contrary to expectation, honey-fed A. iole females matured considerably more eggs when deprived of hosts for 3 or 6 days rather than 0 days. This research suggests that A. iole females are not strictly proovigenic. However, they do have proovigenic tendencies, since most females emerge with at least 71% of their potential fecundity.     

Determinants of egg load in the soybean aphid parasitoid Binodoxys communis

We used a series of laboratory studies to investigate factors contributing to variability in egg load of the parasitoid Binodoxys communis (Gahan) (Hymenoptera: Braconidae), a biological control agent of the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae). The change in egg load in newly emerged females over time was determined in response to three treatments: post‐eclosion temperature, sugar meals, and host density. Binodoxys communis females emerge with an average egg load of approximately 40 mature eggs that increases to approximately 200 eggs within 24 h of emergence. The egg maturation rate over this time period is higher when females are held at 26 °C than at 18 °C. And although the egg load of sugar‐fed females was slightly higher than that of starved females, this difference was not statistically significant. Binodoxys communis females that were held with 150 hosts for 8 h laid more eggs than those that were held with 30 hosts, and they also matured more eggs over the subsequent 16 h than those held with 30 hosts or no hosts at all. However, we detected no difference in the egg maturation pattern between B. communis females held with the low host density and that of control females held with no hosts at all. Thus, we conclude that enhanced egg maturation in the higher host‐density treatment is more likely explained by a rapid replenishing of partially depleted ovaries than a host‐induced stimulus of egg maturation per se. Taken together, these results suggest a strategy of maintaining a high egg load and thus avoiding or mitigating the negative effects of egg limitation.     

State dependent superparasitism in a solitary parasitoid: egg load and survival

In solitary parasitoids, superparasitism (the allocation ofan egg to an already parasitized host) has a payoff, measuredin offspring produced and costs, measured in eggs and time invested.Solitary parasitoids that are capable of host discriminationmust adopt the strategy that ensures the best use of both theiregg load and available lifetime. In this paper, we develop astate-dependent model defining the optimal strategy of superparasitismfor a solitary parasitoid species with overlapping generations.The fitness measure we use is based on the growth rate of thenumber of genotype copies. The model predicts that the tendencyto superparasitize should increase as the egg load of the parasitoidincreases, or as its life expectancy decreases. The model alsopredicts that under particular conditions wasps should showpartial preferences for parasitized hosts. These predictionswere tested with the parasitoid Venturia canescens (Hymenoptera:Ichneumonidae). The tendency of the wasps to superparasitizein the presence of both healthy and parasitized hosts was correlatedto egg load and access to food before the experiment A complementaryexperiment, where parasitized hosts were given sequentiallyto parasitoids, showed that V. canescens exhibits partial preferencestoward superparasitism. These experimental results and a previouswork support the predictions of the model.     

Superparasitism in the solitary ectoparasitoid Aptesis nigrocincta: the influence of egg load and host encounter rate

Theory predicts that the acceptance of hosts already parasitized by a conspecific will depend both on egg load and the availability of hosts. In the present laboratory study, we tested the effect of egg load and host encounter rate on the propensity of superparasitism in the solitary parasitoid Aptesis nigrocincta Gravenhorst (Hymenoptera, Ichneumonidae), a synovigeneous ectoparasitoid of prepupae of the European Apple Sawfly. Parasitoid females carry few voluminous eggs at a time and the egg maturation rate is less than one egg per day. Egg load was manipulated by giving females access to hosts one week prior to the start of treatments and host availability by giving females access to either one host cocoon every day or every other day. In the first treatment where females had a high egg load of 5.3 egg in their ovaries and encountered host cocoons at low rates, we found that parasitized hosts were accepted to the same degree as healthy hosts. In females with significantly decreased egg load (3.8 eggs) encountering hosts at the same rate we found a slight but non‐significant decrease in the acceptance of parasitized hosts compared with healthy hosts. In contrast, A. nigrocincta females accepted significantly fewer parasitized hosts at a high host encounter rate that would lead them to the point of egg limitation in the near future. Within the range of egg loads tested, the host encounter rate appears to be the most important determinant for a females decision to oviposit onto hosts already parasitized by a conspecific.     

Host discrimination modulates brood guarding behaviour and the adaptive superparasitism in the parasitoid wasp Trissolcus semistriatus (Hymenoptera: Scelionidae)

Because hosts utilized by parasitoids are vulnerable to further oviposition by conspecifics, host guarding benefits female wasps. The present study aims to test whether female adults regulate brood guarding behaviour by host discrimination in a solitary parasitoid Trissolcus semistriatus by presenting an intact or parasitized host egg mass to a female adult. Virgin females without oviposition experience have host discrimination ability, which enables them to adjust the number of eggs laid in the hosts. Mating experience increases superparasitism by female adults, whereas mated females achieve a higher discrimination ability as a result of oviposition experience and show a lower superparasitism rate. As expected, females exhibit brood guard after parasitizing an intact host egg mass, whereas those females visiting a previously parasitized host egg mass, do not. Because the survival of eggs in superparasitized hosts is relatively low, regulating brood guarding behaviour by host discrimination is adaptive for female wasps.