Host association in Chrysis fulgida L. and description of its prepupa (Hymenoptera: Chrysididae)

In a study on the host association of the cuckoo wasp, Chrysis fulgida L., at two nesting sites in Northern Italy, it was observed emerging from nests of the mason wasp, Symmorphus crassicornis (Panzer). Although other species of eumenine wasps nested in the same area, none of them was attacked by this parasitoid. Parasitism rate per nest ranged from 0% to 66.3%, 45.8% on average. The number of parasitized cells did not decrease either with the thickness of the nest closing plug or with the length of vestibular cell. No differences in the number of cells per nest or in the length of vestibular cell were found when comparing parasitized and unparasitized nests, suggesting that the wasps probably did not abandon their parasitized nest and that the cuckoo wasp larva was not detected. A review of the host associations of the species of Chrysis of the ignita group suggests that mason wasps are the preferred hosts and that cavity-nesters are more frequently attacked than soil- or mud-nesters. The prepupa of C. fulgida is described, illustrated, and compared with the described mature larvae of Chrysididae. The postdefecating larva of this species exhibits the autapomorphy that defines the genus Chrysis: "normally developed galeae." The most salient character shown by the mature larva of this species lies in the maxillary palpus, which has 6 sensilla at apex. This character state allows this prepupa to be differentiated from the previously described mature larvae of the genus.