The Biology of Acroceridae (Diptera): True Endoparasitoids of Spiders

Abstract

The dipterous parasitoids and predators of spiders are restricted to a few families of Diptera and vary considerably in their mode of action. Members of the families Drosophilidae, Phoridae, Chloropidae, and Sarcophagidae are known to predate on eggs of several families of spiders (Clausen 1940; Eason et al. 1967). Recently, the first endoparasitic member of the family Tachinidae, Lypha sp., was reported to attack the fossorial spider Atypoides riversi in California (Vincent 1985). The only truly coevolved, host-restricted, parasitoid family of Diptera known to attack spiders is the endoparasitic family Acroceridae (Cyrtidae of authors). Although I am convinced that acrocerid larvae attack and develop successfully only in true spiders (Araneae), I should note the case cited by Sferra (1986) where the first instar larvae of Pterodontia flavipes were found internally in the bodies of several types of Acari. However, because of the small size of the hosts, there is no possibility that this parasitoid could develop further. The only real competitor to acrocerids for this endoparasitic mode of life appears with certain nematodes (Poinar, this volume). In fact, Vincent and Schlinger (unpublished notes) recently found a case where the spider, Atypoides riversi was serving as a host for both a nematode and an acrocerid (Eulonchus) larva simultaneously. Which one of these parasitoids (if any) would have been the successful competitor was not determined due to the early dissection of the host.