The Epithelium of the Gut as a Barrier Against Encapsulation By Blood Cells in Three Species of Parasitoids of Bupalus Piniarius (Lep., Geometridae)

Abstract

Three habitual parasites of the pine looper are generally not eliminated by the haemocytic defence reaction of their usual host, because the eggs are laid or the larvae settle behind the epithelium of the gut. This acts as a barrier against the passage of blood cells. This conclusion is supported by the observation that larvae of all three species are encapsulated during abnormally long stays in the host's body cavity. In two species this results from the parasitoid's failure to oviposit in the usual way, being either egg deposition at a less favourable site on the host's integument, or in a less suitable larval instar of the host. In the third species encapsulation results from the failure of the parasitoid's larva to enter the mid-gut due to some unknown factor(s) related to superparasitism.