Parasitoid Cocoons Research Articles

Behavioral Modification of Leucauge mariana Induced by an Ichneumonid Spider-Parasitoid, Hymenoepimecis castilloi, in the Colombian Andes

Hymenoepimecis is a genus of Darwin wasps in the Polysphincta group of genera (Hymenoptera: Ichneumonidae: Pimplinae) known as ectoparasitoids of a broad spectrum of spiders. The parasitoid induces production of a web known as cocoon web, which provides shelter and support for the wasp pupa. In this study, we describe for the first time the interaction between Hymenoepimecis castilloi Pádua & Sääksjärvi (Hymenoptera: Ichneumonidae) and its host spider Leucauge mariana (Taczanowski) (Araneae: Tetragnathidae) in the Colombian Andes, provide new records of wasp genus distribution, and described the behavioral modifications induced in the spider. Web modifications occurred in the webs of both solitary and aggregated individuals. Adhesive spirals were lacking, and webs were connected to vegetation by multiple threads in all cocoon webs, which was not seen attached to webs of non-parasitized spiders. All parasitoid cocoons were observed hanging on a vertical line in the hub of the cocoon web. As previously described for other species, we believe that this modified web design results in increased web strength and favors parasitoid development during the pupal stage.

Host stage and temperature for the rearing of Aridelus rufotestaceus (Hymenoptera: Braconidae), with notes on acceptance and suitability of 2 stink bug species.

Nezara viridula (L.) (Hemiptera: Pentatomidae) is a harmful pest of many agricultural crops in different parts of the world. This stink bug is the preferred host species of Aridelus rufotestaceus Tobias (Hymenoptera: Braconidae), an endoparasitoid of nymphs and adults of pentatomids. With the aim to improve the rearing procedure of this beneficial insect, the acceptance and suitability of all mobile stages of N. viridula (from first instar nymph to adult) were evaluated. At 25 °C, all host stages were accepted and suitable for A. rufotestaceus development, but the highest parasitoid cocoon and adult yields were obtained from second instar nymphs. The possibility to reduce the development time of A. rufotestasceus by increasing the rearing temperature was also evaluated, but 28 °C proved to be detrimental for parasitoid development, as shown by the very low cocoon and adult numbers obtained. The acceptance and suitability of the invasive pentatomid species Halyomorpha halys (Stål) for A. rufotestaceus was also tested. Female wasps were observed piercing H. halys nymphs with the ovipositor, but no cocoons were obtained, nor were larvae or head capsules detected in the exposed stink bugs.

New host plant record, first report of natural parasitisation, report of ‘parasitoid guarding’ behaviour with notes on biology and identification of Thyrassia virescens (Hampson, 1892) (Insecta: Lepidoptera: Zygaenidae)

ABSTRACT Caterpillars of Thyrassia virescens (Hampson, 1892) were collected from a newly recorded host plant Cissus quadrangularis Linnaeus, 1767 (Vitaceae) in Chikaballapura district of Karnataka State in India from June to September 2021. Larvae were reared in room condition to study the life cycle. The total larval period was found to be 18–22 days with four instars. The pupal period was found to be 10–12 days. Parasitisation by Cotesia sp. (Braconidae: Hymenoptera) on the caterpillars of T. virescens has been documented for the first time. While there was no parasitisation occurred during the first generation, the second and third generations showed 93.3% and 18.18% parasitisation respectively. Notes on the identification features such as the male and female genitalia have been described. An interesting ‘parasitoid-guarding’ behaviour has been documented, in which the caterpillars seem to protect the parasitoid cocoon from hyper-parasitoids and other enemies until the emergence of parasitoid adult.

Butterfly–parasitoid–hostplant interactions in Western Palaearctic Hesperiidae: a DNA barcoding reference library

AbstractThe study of ecological interactions between plants, phytophagous insects and their natural enemies is an essential but challenging component for understanding ecosystem dynamics. Molecular methods such as DNA barcoding can help elucidate these interactions. In this study, we employed DNA barcoding to establish hostplant and parasitoid interactions with hesperiid butterflies, using a complete reference library for Hesperiidae of continental Europe and north-western Africa (53 species, 100% of those recorded) based on 2934 sequences from 38 countries. A total of 233 hostplant and parasitoid interactions are presented, some recovered by DNA barcoding larval remains or parasitoid cocoons. Combining DNA barcode results with other lines of evidence allowed 94% species-level identification for Hesperiidae, but success was lower for parasitoids, in part due to unresolved taxonomy. Potential cases of cryptic diversity, both in Hesperiidae and Microgastrinae, are discussed. We briefly analyse the resulting interaction networks. Future DNA barcoding initiatives in this region should focus attention on north-western Africa and on parasitoids, because in these cases barcode reference libraries and taxonomy are less well developed.

Host suitability of Trichoplusia ni and Chrysodeixis chalcites (Lepidoptera: Noctuidae) for native and nonnative parasitoids expanding their host range

AbstractWe evaluated the host suitability and related traits of Trichoplusia ni Hübner (Lepidoptera: Noctuidae) and Chrysodeixis chalcites Esper (Lepidoptera: Noctuidae), which is nonnative in North America, for the native parasitoids Campoletis sonorensis Cameron (Hymenoptera: Ichneumonidae) and Copidosoma floridanum Ashmead (Hymenoptera: Encyrtidae), and the nonnative parasitoid Cotesia vanessae Reinhard (Hymenoptera: Braconidae). For the larval parasitoid C. sonorensis and C. vanessae trials, three-day-old larvae of both hosts were used, whereas one-day-old eggs of both hosts were used for the egg–larval parasitoid C. floridanum trial. For suitability parameters on each host exposed separately to each of the three parasitoid species, we measured parasitoid emergence (parasitoid success), parasitoids that did not emerge (parasitoid cocoon mortality), the proportion of male offspring (parasitoid sex ratio), hosts that developed into moths (host success), hosts that died without developing into moths or producing a parasitoid (host mortality), parasitoids emerging from cocoon masses (brood size), and the developmental times of parasitoids and hosts. For C. sonorensis, the native host and the nonnative host were found to be similarly suitable. For C. vanessae, the native host was more suitable than the nonnative host. For C. floridanum, the native host was suitable, whereas the nonnative host was not; however, sublethal effects on both the native and nonnative hosts were observed. The differential suitability of the hosts observed in this study contributes to the understanding of this measure as a dynamic factor in the expansion of parasitoids into novel host species.

Differential effects of climate warming on reproduction and functional responses on insects in the fourth trophic level

Abstract Understanding the effects of anthropogenic global warming (AGW) on species interactions is essential for predicting community responses to climate change. However, while effects of AGW on resource–consumer interactions at the first and second trophic level have been well studied, little is known about effects on interactions at higher trophic levels at the terminal end of food chains (e.g. in the third and fourth trophic levels). Here, we examined the effects of temperature variability by simulating heatwaves on functional responses of two species at the fourth trophic level (hyperparasitoids) that parasitize host species at the third trophic level (parasitoid cocoons). We found that host cocoons developed faster under simulated heatwave conditions, decreasing the temporal window of susceptibility of the host cocoons to parasitism by the two hyperparasitoids, and consequently parasitism declined with temperature. However, the effects of a simulated heatwave markedly differed among the two hyperparasitoid species; temperature and host quality had a much stronger effect on early reproduction in the less fecund hyperparasitoid Gelis agilis, than in the more fecund species Acrolyta nens. Our results suggest that exposure to heatwaves, that are expected to increase in frequency, will affect the ability of species at higher trophic levels to exploit transient resources whose suitability is temperature‐dependent. In turn, the observed effects of AGW on the functional responses of the hyperparasitoids may disrupt trophic interactions and have profound impact on population dynamics and ecological processes. A plain language summary is available for this article.

Interspecific competition among Cotesia kazak, Microplitis croceipes, and Meteorus pulchricornis (Hymenoptera: Braconidae), larval parasitoids of Helicoverpa armigera (Lepidoptera: Noctuidae) in New Zealand

Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae) is a polyphagous parasitoid known to have an extremely wide host range, attacking larvae from at least 11 lepidopteran families. It was first detected in New Zealand in 1996 and spread rapidly, raising concerns that it may disrupt an integrated pest management program for Helicoverpa armigera (Hübner) that relied on two introduced larval parasitoids: Cotesia kazak and Microplitis croceipes. A series of laboratory experiments was undertaken to assess larval competition among these three parasitoid species. H. armigera larvae were exposed to the three parasitoid species in pairwise combinations and the subsequent formation of parasitoid cocoons and emergence of adults were recorded. Separate assays were run with 0, 24 and 48h time intervals between ovipositions by each wasp species. The results showed that C. kazak prevailed over M. pulchricornis and M. croceipes in all experimental combinations and time intervals, accounting for 79–100% of parasitoid cocoons, and that M. pulchricornis was similarly dominant over M. croceipes. The observed dominance of C. kazak in processing tomato crops in New Zealand may be partly explained by the competitive advantage of its larvae, combined with a reportedly faster development rate. However, the nature of the competitive relationship between these species may well be modified by extrinsic factors in the field. In particular, M. pulchricornis may gain an advantage in more diverse cropping systems where it may exploit alternative hosts that are not suitable for the other species.

Host behaviour manipulation as an evolutionary route towards attenuation of parasitoid virulence.

By definition, insect parasitoids kill their host during their development. Data are presented showing that ladybirds not only can survive parasitism by Dinocampus coccinellae, but also can retain their capacity to reproduce following parasitoid emergence. We hypothesize that host behaviour manipulation constitutes a preadaptation leading to the attenuation of parasitoid virulence. Following larval development, the parasitoid egresses from the host and spins a cocoon between the ladybird's legs. Throughout parasitoid pupation, the manipulated host acts as a bodyguard to protect the parasitoid cocoon from predation. The parasitoid has evolved mechanisms to avoid killing the host prematurely so that its own survival is not compromised. Bodyguard manipulation may thus constitute a selective trait for the evolution of true parasitism in some host-parasitoid associations.

A bodyguard or a tastier meal? Dying caterpillar indirectly protects parasitoid cocoons by offering alternate prey to a generalist predator

AbstractIn some parasitic Hymenoptera the dying caterpillars remain attached or close to the parasitoid cocoons. It has been suggested that the caterpillars act as ‘bodyguards’ for the vulnerable cocoons and therefore protect them against predators and/or hyperparasitoids (the ‘usurpation hypothesis’). This hypothesis has been demonstrated in associations where the caterpillars remain active and/or aggressive after parasitism. However, in other associations the caterpillars are so physiologically depleted after parasitism that they are unable to physically defend the cocoons and instead sit atop them in a moribund state. In this study a generalist predator, the spined soldier bug, Podisus maculiventris Say (Hemiptera: Pentatomidae), was provided with cocoons of the gregarious endoparasitoid Cotesia glomerata L. and the solitary endoparasitoid Microplitis mediator Haliday (both Hymenoptera: Braconidae), in turn attended by their hosts, Pieris brassicae L. (Lepidoptera: Pieridae) and Mamestra brassicae L. (Lepidoptera: Noctuidae), respectively. Cotesia glomerata produces broods of up to 40 cocoons and the dying caterpillars sit atop the cocoons where they exhibit little response to physical stimuli. Previous studies reported that dying P. brassicae caterpillars were ineffective bodyguards against two species of hyperparasitoids. In both associations, the dying host caterpillars were significantly preferred as food by P. maculiventris over the parasitoid cocoons. However, in absence of caterpillars, the bugs readily attacked the C. glomerata cocoons. Alternatively, the survival of M. mediator was very low, irrespective of whether a caterpillar was present or not. Caterpillars attacked by M. mediator are several times smaller than those attacked by C. glomerata. Consequently, the predators ran out of food much more quickly in the former and switched from one prey to the other. We show that in some host–parasitoid associations the dying caterpillars provide more visually apparent or nutritionally superior prey, rather than acting as bodyguards.

A Simple Method for Estimating Instantaneous Levels of Endoparasitism ofPlutellaxylostella(Linnaeus) (Lepidoptera: Plutellidae) by Hymenoptera in the Field

Although endoparasitoids are widely used for biological control of Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) throughout the world, current methods do not allow for easy estimation of parasitism levels. I investigated the potential of using ratios of parasitoid cocoons to infestations to develop a simple and practical method of estimating parasitism levels in the field. Crop infestations by the pest and densities of its endoparasitoids' cocoons were recorded at weekly intervals over six consecutive years on unsprayed cabbage. In order to establish if there was a relationship between parasitism levels and ratios of parasitoid cocoons to infestations, samples of host larvae and pupae were collected every week during scouting for rearing in the laboratory. The majority of parasitoid cocoons belonged to the larval endoparasitoid Cotesia vestalis (Haliday) (Hymenoptera: Braconidae), which was the major mortality factor of P. xylostella. Total parasitism levels were positively related to ratios of parasitoid cocoons to infestations. Crop infestation by P. xylostella was low during periods of high parasitism (≥50 %) than during low parasitism (< 50 %), and 50 % parasitism corresponded with 20 % ratio of parasitoid cocoons to infestations. This study shows that ratios of parasitoid cocoons to infestations can be used to estimate background parasitism levels.

Examination and revision of the larval life history of Microplitis croceipes (Hymenoptera: Braconidae)

Microplitis croceipes (Braconidae) is a solitary parasitoid of Heliothis virescens (Noctuidae), the tobacco budworm. The larva of M. crocepies develops within the abdominal cavity of its host while the host remains active. Larval development culminates with egression of the larva from its host, and subsequent cocoon spinning and pupation near the host’s body. Previous research indicated that M. croceipes larvae pass through three instars within the host, followed by egression and pupation. Head capsule measurements recorded in this study at several intervals during larval development revealed that the larvae of M. croceipes pass through five instars. The final molt, i.e. into the fifth instar, occurs during larval egression from the host, and the shed exuvium remains lodged in the egression wound, acting as a plug that prevents exsanguination of the host. The host remains alive through parasitoid pupation, and may play a defensive role guarding the parasitoid cocoon during its development to the adult stage.

Bodyguard manipulation in a multipredator context: Different processes, same effect

Parasites have evolved various strategies to exploit hosts to their own advantage. Bodyguard manipulations consist of usurping the behaviour of the host to confer some protection to the parasite and/or its offspring. Dinocampus coccinellae Schrank is a solitary endoparasitoid of the spotted lady beetle Coleomegilla maculata lengi Timberlake. The parasitoid larva grows inside the host until mature, then egresses and spins a cocoon between the ladybird's legs. Unlike most parasitoids, D. coccinellae does not kill its host during development, but keeps the coccinellid partially paralysed on top of the cocoon, where it acts as a bodyguard against natural enemies. As recently shown, the presence of a living ladybird on the parasitoid cocoon provides efficient protection against a predator, lacewing larvae. In the present study, we used predators with different foraging behaviours—jumping spiders and crickets—to explore the relevance of the bodyguard strategy for D. coccinellae in a multipredator context. Although the manner of the protection differs among the different tested predators, the presence of the ladybird always enhances parasitoid survival, even when it first increases detection of the cocoon–ladybird complex, as is the case with jumping spiders. Furthermore, although a dead bodyguard is sufficient to passively defend parasitoid cocoons against crickets, it provides only partial protection against jumping spiders. Altogether, these results support the bodyguard hypothesis in a multipredator context, since the presence of a living coccinellid significantly reduces cocoon predation by predators having different prey specificities, morphologies, and hunting behaviours.

The relationship between the diamondback moth, climatic factors, cabbage crops and natural enemies in a tropical area

ABSTRACT The impact of abiotic and biotic factors (rainfall, temperature, host plant and natural enemies) on population dynamics of the Plutella xylostella L. diamondback moth was investigated. The experiments were conducted during the rainy and dry seasons for two years (June 2009-April 2011) on unsprayed cabbage plots in Malika (Senegal). Every 10 days, 10 cabbages were randomly selected. Plutella xylostella larvae, pupae and parasitoid cocoons were recorded on each plant. Before each sampling, the diameters and ages of plants were recorded. Temperature and rainfall were also recorded during this study. Larvae and pupae of P. xylstella were higher for the dry season than the rainy season. There was a negative correlation between temperature and P. xylostella populations, and a strong relationship between P. xylostella populations and the age of cabbages. Females oviposited on young cabbages where the presence of young larvae was important, whereas older immature stages were mainly found in older cabbage plants. Parasitoid populations were higher for the dry season than the rainy season. High temperatures did not increase the pest populations and parasitism rate. There was no effect found on pest, plants and natural enemies due to rainfall. There was a positive correlation between pest populations and parasitism. Four Hymenoptera species were found: Oomyzus sokolowskii, Apanteles litae, Cotesia plutellae and Brachymeria citrae, but they were not efficient to control the P. xylostella populations. These results are important for understanding the factors that promote or inhibit pest populations and their natural enemies, and therefore essential for effective crop protection.

Lampides Boeticus (Lepidoptera: Lycaenidae) Preys on Cocoons of its Own Specific Parasitoid Cotesia Specularis (Hymenoptera: Braconidae)

We present observations and experimental evidence for a new type of parasitoid-host interaction. In the Lampides boeticus (Lepidoptera) - Cotesia specularis (Hymenoptera) system, larvae of the former species readily kill and consume the parasitoid cocoons they find. Potential effects at both the individual and population levels are briefly outlined.

Differing Success of Defense Strategies in Two Parasitoid Wasps in Protecting their Pupae Against a Secondary Hyperparasitoid

Abstract During their larval development, endoparasitoids are known to dispose of host resources in several different ways. Some parasitoid wasps consume most or all tissues of the host, whereas others consume a small fraction of host resources and either ensure that the host moves away from the pupation site or allow the host to remain close to the parasitoid cocoon(s). Using a single host species, Mythimna separata Walker (Lepidoptera: Noctuidae), this study compares the success of the two pupation strategies in the solitary parasitoids Microplitis sp. and Meteorus pulchricornis Wesmael (Hymenoptera: Braconidae) against attack from a secondary hyperparasitoid, Gelis agilis F. (Hymenoptera: Ichneumonidae). The caudal appendages of M. separata caterpillars parasitized by Microplitis sp. remain physically attached to parasitoid cocoons and the caterpillars behave aggressively when disturbed. However, after Me. pulchricornis larvae emerge from caterpillars of their host, M. separata, the parasitoid larvae pupate in cocoons that are suspended by a single thick thread that hangs 1–2 cm from under a leaf. In choice tests conducted in petri dishes, significantly fewer cocoons of Microplitis sp. attended by caterpillars than unattended cocoons were hyperparasitized by G. agilis. By contrast, Me. pulchricornis cocoons that were hanging from corn, Zea mays L., plants were hyperparasitized as frequently as those which were attached to leaves. We discuss the potentially different selection pressures generated among natural enemies such as predators and hyperparasitoids in determining optimal pupal defense strategies in primary parasitoids.

The ‘usurpation hypothesis’ revisited: dying caterpillar repels attack from a hyperparasitoid wasp

It has been posited that some parasitoid wasps ‘usurp’ their dying hosts as ‘bodyguards’ to protect the vulnerable parasitoid cocoons against attack from natural enemies such as predators or hyperparasitoids. Thus far, however, the hypothesis has been supported only in studies with insect predators. Two factors may account for this: first, hyperparasitoids, being more specialized than predators, are probably less easily rebuffed by the presence of an attending caterpillar; second, the host cocoon is used for reproduction by hyperparasitoids, but not by predators. We compared the survival of a solitary primary parasitoid, Microplitis sp., and successful parasitism by a secondary hyperparasitoid, Gelis agilis, from parasitoid cocoons with and without the presence of an ‘attending’ larva of the host, the armyworm, Mythimna separata. Mature Microplitis sp. larvae always emerge through the same host segment, leaving the posterior segments paralysed and attached to cocoons and the anterior segments freely moving. When disturbed by G. agilis females, M. separata larvae exhibited aggressive behaviour that repeatedly drove off approaching hyperparasitoids. In choice and no-choice experiments performed at 24 h intervals over 96 h, G. agilis successfully parasitized cocoons without attending caterpillars, but few cocoons with attending caterpillars were ever parasitized. Choice experiments, in which G. agilis wasps were released onto corn plants containing 24 h-old parasitoid cocoons with and without attending caterpillars, produced similar results. We provide the first experimental evidence that a solitary parasitoid usurps the behaviour of its host over several days as a ‘bodyguard’ against hyperparasitoids.

Leluthia astigma(Ashmead) (Hymenoptera: Braconidae: Doryctinae) as a Parasitoid ofAgrilus planipennisFairmaire (Coleoptera: Buprestidae: Agrilinae), with an Assessment of Host Associations for Nearctic Species ofLeluthiaCameron

Published host associations are assessed for Leluthia astigma (Ashmead), Leluthia floridensis Marsh, and Leluthia mexicana Cameron, the three known species of Leluthia Cameron in the Nearctic Region. Leluthia astigma is reported as a parasitoid of Agrilus planipennis Fairmaire, emerald ash borer (EAB), infesting Fraxinus americana L., white ash, in Delaware County, Ohio. It is the first species of Leluthia for which a determined species of Agrilus Curtis has been confirmed as a host and the association vouchered. All other hosts reported in the literature for L. astigma require confirmation through rearing from an isolated host or documentation of an unequivocal host-parasitoid association. Leluthia astigma adults reared from parasitoid cocoons collected in Delaware County, Ohio parasitized and produced F1 adults in the laboratory on last-instar EAB larvae collected in Ingham County, Michigan. Parasitism of EAB and other natural history data are reported for L. astigma, including the first records of L. astigma from Kansas and New York.

Comparing the physiological effects and function of larval feeding in closely‐related endoparasitoids (Braconidae: Microgastrinae)

Abstract The larvae of most endoparasitoid wasps consume virtually all host tissues before pupation. However, in some clades, the parasitoid larvae primarily consume haemolymph and fat body and emerge through the side of the host, which remains alive and active for up to several days. The evolutionary significance of this host‐usage strategy has attracted attention in recent years. Recent empirical studies suggest that the surviving larva guards the parasitoid broods against natural enemies such as predators and hyperparasitoids. Known as the ‘usurpation hypothesis’, the surviving larvae bite, regurgitate fluids from the gut, and thrash the head capsule when disturbed. In the present study, the ‘usurpation hypothesis’ is tested in the association involving Manduca sexta, its parasitoid Cotesia congregata, and a secondary hyperparasitoid Lysibia nana. Percentage parasitoid survival is higher and hyperparasitism lower when cocoons of C. congregata are attached to the dorsum of M. sexta caterpillars. Fat body contents in several associations involving solitary and gregarious parasitoids feeding on haemolymph and fat body are also compared. The amount of fat body retained in parasitized caterpillars varies considerably from one association to another. In M. sexta and Pieris brassicae, considerable amounts of fat body remain after parasitoid emergence whereas, in Cotesia kariyai and Cotesia rufricus, virtually all of the fat body is consumed by the parsasitoid larvae. The length of post‐egression survival of parasitized caterpillars differs considerably in several tested associations. In Pseudeletia separata, most larvae die within a few hours of parasitoid emergence whereas, in M. sexta, parasitized larvae live up to 2 weeks after parasitoid emergence. Larvae in other associations parasitized by gregarious and solitary endoparasitoids live for intermediate periods. The results are discussed in relation to the adaptive significance of different feeding strategies of immature parasitoids and of the costs and benefits of retaining the parasitized caterpillar in close proximity with the parasitoid cocoons.

Do parasitized caterpillars protect their parasitoids from hyperparasitoids? A test of the ‘usurpation hypothesis’

Caterpillars that are attacked by some species of parasitoid wasps are known to survive for several days after the parasitoid larvae emerge and pupate. It has been argued that the behaviour of the parasitized larva is ‘usurped’ by the parasitoid and that it ‘guards’ the parasitoid cocoons against their own natural enemies such as hyperparasitoids (the ‘usurpation hypothesis'). We tested this hypothesis in the association involving a gregarious endoparasitoid, the wasp Cotesia glomerata; caterpillars of its host, the large cabbage white butterfly Pieris brassicae; and a pupal hyperparasitoid, the wasp Lysibia nana. In laboratory experiments, we presented cocoon broods of C. glomerata to single females of L. nana in arenas for 6 h. We tested several treatments for rates of primary parasitoid survival, including variation in the position of the caterpillar and the presence or absence of an additional silk web spun by parasitized caterpillars. Parasitized P. brassicae larvae survived longer than the period necessary for C. glomerata adults to emerge. Rates of parasitoid survival were, however, unaffected by the presence of a P. brassicae larva on the cocoon brood, although significantly more parasitoids emerged when the silk web was present. Analyses of the foraging behaviour of individual L. nana females in arenas, performed using Observer software, revealed that the wasps showed a greater tendency to leave cocoons when caterpillars and silk were present. The laboratory experiments only partially support the usurpation hypothesis. In nature, usurpation of the host of the primary parasitoid may be a more effective strategy against generalist predators than against more specialized and better-adapted hyperparasitoids.

Compatibility of Endoparasitoid &lt;I&gt;Hyposoter didymator&lt;/I&gt; (Hymenoptera: Ichneumonidae) Protected Stages with Five Selected Insecticides

Hyposoter didymator (Thunberg) (Hymenoptera: Ichneumonidae) is a koinobiont endoparasitoid that emerges from the parasitization of economically important noctuid pests. H. didymator also is considered one of the most important native biocontrol agents of noctuids in Spain. Side effects of five insecticides with very different modes of action (fipronil, imidacloprid, natural pyrethrins + piperonyl butoxide, pymetrozine, and triflumuron) at the maximum field recommended rate in Spain were evaluated on H. didymator parasitizing Spodoptera littoralis (Boisduval) larvae and pupae of the endoparasitoid. Parasitized larvae were topically treated or ingested treated artificial diet. Parasitoid cocoons were topically treated. Host mortality when parasitized larvae were treated, as well as further development of the parasitoid surviving (e.g., percentage of cocoons spun, adult emergence, hosts attacked, and numbered progeny) were determined. Toxicity after treatment of parasitized larvae differed depending on the mode of exposure and insecticide. Fipronil was always highly toxic; imidacloprid killed all host insects by ingestion, but it was less toxic to both host and parasitoids, when administered topically; natural pyrethrins + piperonyl butoxide and triflumuron showed differing degrees of toxicity, and pymetrozine was harmless. Parasitoid cocoons provided effective protection against all the insecticides, except fipronil.