Morphology and ultrastructure of the cephalic vesicles in two species of the Gonatopus genus: Gonatopus camelinus Kieffer and Gonatopus clavipes (Thunberg) (Hymenoptera, Dryinidae, Gonatopodinae)

The cephalic vesicles of the immature endo-ectoparasitic larvae of Gonatopu s camelinus Kieffer and Gonatopus clavipes (Thumberg) were studied using li ght and electron microscopy. The vesicles appear as hollow evaginations of the cephalic body wall and their tegument consists of a monolayered epithel ium externally surrounded by a permeable cuticle. In the first larval insta rs, the epithelial cells are pyramid-shaped and separated by large intercel lular spaces. In the last larval instars they are polyhedral and the interc ellular spaces are no longer evident. The vesicles have no connection with the gut of either the host or the larva. These data suggest that nutrients are absorbed by the dryinid larva from the haemolymph of the host through t he permeable surface of the cephalic vesicles, where they are stored in the lumen and enter the larval haemolymph without passing through the gut. In all immature larval instars the mouth is closed.