Polistes dominulus wasps (Hymenoptera Vespidae), if parasitized by Xenos vesparum (Strepsiptera Stylopidae), wander among nests during the pre-emergence phase

This study is focused on the spatial behaviour of overwintered Polistes dominulus wasps, either unparasitized or parasitized by Xenos vesparum (Strepsiptera). The neotenic female endoparasites protrude their cephalothorax from the host abdomen and, after winter diapause, hundreds of 1(st) instar larvae, the infective free-living stage, emerge alive and move from the brood canal of the cephalothorax to the substrate. We carried out spring transects along artificial hibernation/nesting sites showing a high site-attachment of healthy wasps before and mainly after nest foundation, whereas parasitized ones moved from one colony to another just when wasp larvae, the target of infection, are present in nests. These data support the hypothesis of a direct release of Xenos larvae on/close to nests although phoresy, assumed as the usual infection mechanism for Strepsipterans, is also possible. RI Massolo, Alessandro/I-3437-2012