Divergence in host utilisation by two spider ectoparasitoids within the genus Eriostethus (Ichneumonidae, Pimplinae)

Our study revealed considerable differences in host-parasitoid interactions between Eriostethus minimus associated with 3D tangle web-building spiders from the family Theridiidae (new family record for Eriostethus) and E. perkinsi associated with 2D orb-web weaving spiders from the family Araneidae. A pupa of the former species was located in a spider retreat in the centre of an unmodified 3D tangle web and the pupal cocoon had a sparsely woven and partially transparent wall. In contrast, a cocoon of the latter species was suspended at the centre of a modified irregular sparse 3D cocoon web and the pupal cocoon had a strong, densely woven cocoon wall. This difference in host utilisation is not in agreement with the synonymisation of Millironia with Eriostethus.