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If the risk of larval competition is high and its consequence on offspring mortality is important, we expect female behavioural strategies favouring the survival of their offspring to be selected for. In parasitoids, hosts can be parasitized several times, in some cases by females of different species (i.e., multiparasitism). In solitary parasitoids, only one offspring can develop per host: supernumerary individuals are eliminated through larval competition. Under these conditions, mothers can lay additional eggs in/on the same host (i.e., self‐superparasitism) to increase the chances of one of their offspring winning the competition. They can also aggressively protect their offspring against competing females to prevent them from multiparasitism and ovicide. Both strategies (self‐superparasitism and host defence) are observed in females of the solitary ectoparasitoid wasp, Dinarmus basalis Rondani (Hymenoptera: Pteromalidae), when facing females of another solitary ectoparasitoid species, Eupelmus vuilleti (Hymenoptera: Eupelmidae), during host exploitation. Here, we aimed to explore whether D. basalis females' behaviours relate to their offspring survival chances during larval competition: we expect mothers to defend their hosts only during the vulnerability period of their offspring and self‐superparasitize to increase the chances of their offspring winning the larval competition. We thus measured the effect of oviposition order (D. basalis females oviposited first or second), delay between ovipositions (30–60 min or 3–4 h) and the occurrence of D. basalis females' self‐superparasitism on D. basalis offspring survival when competing with E. vuilleti juveniles. Our results showed D. basalis offspring constantly had a lower survival probability than E. vuilleti offspring. Only being laid first increased D. basalis offspring survival rate, whereas the time delay between ovipositions and self‐superparasitism did not significantly increase it further. The fact that offspring survival chances under interspecific competition may not be the main driver of maternal host protection and self‐superparasitism is discussed. [ABSTRACT FROM AUTHOR]

Globally, Anastatus species (Hymenoptera: Eupelmidae) are associated with the invasive agricultural pest Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). In Europe, the polyphagous Anastatus bifasciatus (Geoffroy) is the most prevalent native egg parasitoid on H. halys eggs and is currently being tested as a candidate for augmentative biological control. Anastatus bifasciatus frequently displays behavior without oviposition, and induces additional host mortality through oviposition damage and host feeding that is not measured with offspring emergence. This exacerbates accurate assessment of parasitism and host impact, which is crucial for efficacy evaluation as well as for pre‐ and post‐release risk assessment. To address this, a general Anastatus primer set amplifying a 318‐bp fragment within the barcoding region of the cytochrome oxidase I (COI) gene was developed. When challenged with DNA of three Anastatus species —A. bifasciatus, Anastatus japonicus Ashmead, and Anastatus sp.—, five scelionid parasitoid species that might be encountered in the same host environments and 11 pentatomid host species, only Anastatus DNA was successfully amplified. When applied to eggs of the target host, H. halys, and an exemplary non‐target host, Dendrolimus pini L. (Lepidoptera: Lasiocampidae), subjected to host feeding, no Anastatus amplicons were produced. Eggs of the two host species containing A. bifasciatus parasitoid stages, from 1‐h‐old eggs to pupae, and emerged eggs yielded Anastatus fragments. Confirmation of parasitoid presence with dissections and subsequent PCRs with the developed primer pair resulted in 95% success for 1‐h‐old parasitoid eggs. For both host species, field‐exposed sentinel emerged eggs stored dry for 6 months, 100% of the specimens produced Anastatus amplicons. This DNA‐based screening method can be used in combination with conventional methods to better interpret host‐parasitoid and parasitoid‐parasitoid interactions. It will help address ecological questions related to an environmentally friendly approach for the control of H. halys in invaded areas. [ABSTRACT FROM AUTHOR]

Anastatus disparis ( Ruschka) ( Hymenoptera: Eupelmidae) is an egg parasitoid and considered a potential biological control agent of the gypsy moth, Lymantria dispar (L.) ( Lepidoptera: Lymantriidae). Only male offspring of A. disparis emerge from single eggs of L. dispar in the laboratory, and A. disparis exhibits low parasitism on L. dispar in the field. We therefore selected several lepidopteran species with various body sizes to evaluate the optimal egg size for hosting A. disparis. In addition, we explored whether the nutritional content of a single L. dispar egg influences the sex of A. disparis offspring and why female offspring can be reared from L. dispar eggs in the field. The results indicated that host egg size decisively influenced the body size and sex ratio of the parasitoid offspring. Therefore, larger hosts, especially the largest eggs of Antheraea pernyi Guérin-Méneville ( Saturniidae), might increase the fitness of A. disparis females. Lymantria dispar eggs concealed in the larger egg shell of A. pernyi produced female A. disparis, suggesting that adult A. disparis should prefer hosts with larger bodies and that the nutritional content of L. dispar eggs did not play a decisive role in the sex allocation of A. disparis. The results also indicated that the egg mass and the fur cover of L. dispar egg masses might be the key factors inducing female A. disparis to lay female offspring in L. dispar eggs. [ABSTRACT FROM AUTHOR]

This study was designed to indentify novel bioactive molecules in the venom of the parasitoid Eupelmus urozonus Dalman ( Hymenoptera: Eupelmidae). Parasitism by E. urozonus induces apparent paralysis in the larvae of the host Ceratitis capitata ( Wiedemann) ( Diptera: Tephritidae) and it arrests the development of host pupae. Parasitoid eggs were transferred from stung to unparasitized host pupae to determine whether adult female stings or bites from the first instars were responsible for the above effects. The two treatments gave the same results, indicating that both parasitoid adults and larvae produced venoms capable to compromise host development. A protocol was developed to artificially microinject E. urozonus venom into healthy host pupae and adults at known concentrations to study the effects. The microinjection of venom was found to produce the same macroscopic result as natural parasitization, indicating that host developmental arrest was caused by molecules produced by the parasitoid venom glands. One-tenth, one-twentieth, and one-hundredth of the contents of a female venom reservoir was sufficient to compromise the development of 100, 90, and 50% of the microinjected host pupae, respectively. The microinjection of 0.1 female venom equivalents into host adults always caused death within 24 h. Extraction and freezing did not affect the activity of the E. urozonus venom, which facilitates its storage, whereas denaturation treatments demonstrated that the bioactive molecules were proteins. The venom was also found to prevent the hosts from decaying for over 2 weeks and it promoted the accumulation of unknown subspherical granules in the host haemocoel. These results suggest the potential identification of novel molecules with interesting biological activity with various possible applications. [ABSTRACT FROM AUTHOR]

Most parasitoid female wasps can distinguish between unparasitized and parasitized hosts and use this information to optimize their progeny and sex allocation. In this study, we explored the impact of mating on oviposition behaviour (parasitism and self- and conspecific superparasitism) on both unparasitized and already parasitized hosts in the solitary parasitoid wasp Eupelmus vuilleti (Crw.) (Hymenoptera: Eupelmidae). Virgin and mated females had the same oviposition behaviour and laid eggs preferentially on unparasitized hosts. The sex ratio (as the proportion of females) of eggs laid by mated females in parasitism and conspecific superparasitism was 0.67 ± 0.04 and 0.57 ± 0.09, respectively. Likewise, females laid more eggs in conspecific superparasitism than self-superparasitism under our experimental conditions. These experiments demonstrate that E. vuilleti females can (i) discriminate between unparasitized and parasitized hosts and adapt the number of eggs they lay accordingly, and (ii) probably discriminate self from conspecific superparasitized hosts. Finally, mating does not appear to influence the host discrimination capacity, the ovarian function, or the oviposition behaviour. [ABSTRACT FROM AUTHOR]