Behavioral manipulation of host caterpillars by the primary parasitoid waspCotesia glomerata(L.) to construct defensive webs against hyperparasitism

Abstract

Many parasitoids control the behavior of their hosts to achieve more preferable conditions. Decreasing predation pressure is a main aim of host manipulation. Some parasitoids control host behavior to escape from their enemies, whereas others manipulate hosts into constructing defensive structures as barriers against hyperparasitism. Larvae of the parasitoid wasp Cotesia glomerata form cocoon clusters after egression from the parasitized host caterpillar of the butterfly Pieris brassicae. After the egression of parasitoids, the perforated host caterpillar lives for a short period and constructs a silk web that covers the cocoon cluster. We examined whether these silk webs protect C. glomerata cocoons against the hyperparasitoid wasp Trichomalopsis apanteroctena. In cocoon clusters that were not covered by silk webs (''bare'' clusters), only cocoons hidden beneath others avoided hyperparasitism. In covered cocoon clusters, both cocoons hidden beneath others and those with a space between them and the silk web avoided hyperparasitism, whereas cocoons that contacted the silk webs were parasitized. The frequency of cocoons that were hidden beneath others increased with the increasing number of cocoons in a cluster, but the defensive effect of cluster size was thought to be lower than that of silk webs. However, the rate of hyperparasitism did not differ between covered and bare clusters when we allowed the hyperparasitoids to attack the cocoon clusters in an experimental arena. This result was thought to have been caused by low oviposition frequency by these hyperparasitoids. As a result, silk webs did not guard the cocoons from hyperparasitoids in our experiments, but would protect cocoons under high hyperparasitism pressure by forming a space through which the ovipositors could not reach the cocoons.

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

“…Previous experiments examining the function of retaining the use of the dying caterpillar have generally argued that it acts as a 'bodyguard' against predators and/or hyperparasitoids (the 'usurpation hypothesis'; Brodeur & Vet, 1994;Tanaka & Ohsaki, 2006, 2009Grosman et al, 2008;Harvey et al, 2008aHarvey et al, ,b, 2011Maure et al, 2011). However, the level of physical activity exhibited by parasitized caterpillars varies dramatically from one host-parasitoid association to another.…”

“…In combination, these enemies can greatly reduce populations of parasitoids in the field (H€ oller et al, 1993). The parasitoids produce cocoons that may be physically attached to the host dorsum (Kester & Jackson, 1996;Harvey et al, 2008a) or else are placed under or very close to the host (Tanaka & Ohsaki, 2006, 2009Grosman et al, 2008;Harvey et al, 2008bHarvey et al, , 2011. The parasitoids produce cocoons that may be physically attached to the host dorsum (Kester & Jackson, 1996;Harvey et al, 2008a) or else are placed under or very close to the host (Tanaka & Ohsaki, 2006, 2009Grosman et al, 2008;Harvey et al, 2008bHarvey et al, , 2011.…”

“…The hypothesis has been empirically tested in several host-parasitoid systems using predators and hyperparasitoids but has generated only mixed support. By contrast, dying caterpillars of the large cabbage white butterfly, Pieris brassicae L. (Lepidoptera: Pieridae), provided little physical protection for the parasitoid cocoons against two species of solitary hyperparasitoids (Tanaka & Ohsaki, 2006;Harvey et al, 2008b). Harvey et al (2008aHarvey et al ( , 2011 similarly found that parasitoid cocoons exhibited higher survival against hyperparasitoids when attended by dying caterpillars.…”

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

“…Several studies have shown that retaining the use of the surviving host as a "bodyguard" is an effective strategy against hyperparasitoids (Harvey et al 2008a,b) and predators (Kester andJackson 1996, Grosman et al 2008). However, the results of other studies have been less conclusive (Tanaka and Ohsaki 2006). A recent study also reported that M. pulchricornis cocoons that were suspended from threads suffered lower predation from ants than cocoons that were attached to the leaf surface (Shirai and Maeto 2007).…”

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

“…They manipulate the behaviour as well as biochemical and physiological characteristics of their hosts (Fritz 1982;Brodeur and McNeil 1992;Eberhard 2000;Tanaka and Oshaki 2006) to improve their chances of survival.…”