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A bodyguard or a tastier meal? Dying caterpillar indirectly protects parasitoid cocoons by offering alternate prey to a generalist predator
Author(s) -
Harvey Jeffrey A.,
Weber Daniela,
Clercq Patrick,
Gols Rieta
Publication year - 2013
Publication title -
entomologia experimentalis et applicata
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 83
eISSN - 1570-7458
pISSN - 0013-8703
DOI - 10.1111/eea.12127
Subject(s) - biology , caterpillar , parasitoid , parasitism , predation , predator , zoology , generalist and specialist species , larva , host (biology) , botany , toxicology , ecology , habitat
In some parasitic H ymenoptera 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, P odisus maculiventris S ay ( H emiptera: P entatomidae), was provided with cocoons of the gregarious endoparasitoid C otesia glomerata L . and the solitary endoparasitoid M icroplitis mediator H aliday (both H ymenoptera: B raconidae), in turn attended by their hosts, P ieris brassicae L . ( L epidoptera: P ieridae) and M amestra brassicae L . ( L epidoptera: N octuidae), respectively. C otesia 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.