A bionomic overview of spider parasitoids and pseudo-parasitoids of the ichneumonid wasp subfamily Pimplinae
The parasitoid way of life (parasitizing and finally killing a single arthropod host) is one of the most successful lifeways in the animal kingdom, sparking an explosive diversification and accompanying numerous parasitoid strategies in insects, especially in the order Hymenoptera. Amongst parasitoid wasps, the Polysphincta group of genera has evolved a highly distinctive parasitoid mode of life, as solitary koinobiont ectoparasitoids of spiders (Chelicerata: Araneae). Some species of polysphinctine wasps have a remarkable ability to control spiders’ web-building behaviour (host web manipulation) to protect the vulnerable wasp cocoons. The group currently consists of 25 genera and 294 extant species worldwide, with 14 genera known to manipulate their host spiders. This study reviews the current species composition, distribution, host utilization and biology of all genera belonging to the Polysphincta group and their ancestral genera of spider egg mass pseudo-parasitoids, highlighting specific offensive approaches for subjugating spider hosts for oviposition and web manipulation against specific spider hosts. There must still be many more unique behaviours to be discovered, given that the life histories of several polysphinctine genera are poorly known or unknown. A tidy correspondence between lineages of polysphinctines and host spiders was recognized, implying the evolutionary history of polysphinctines. Based on the integrated information on behavioural data and host utilization, we suggest some hypotheses determining triggers for host shifts and discuss the possibility of adaptive radiation driven by divergent natural selection on host differentiation. One new taxonomic change is proposed: Zaglyptus idukkiensis (Manjusha, Sudheer & Ghosh, 2019), comb. nov., is transferred from Polysphincta.