Parasitization Biology of a New Species of Braconidae (hymenoptera) Feeding on Larvae of Costa Rican Dry Forest Skippers

– The black and red medium-sized parasitoid wasp Bassus brooksi Sharkey n. sp. (Braconidae) is described from wild-caught specimens from dry forest habitats ranging from northern Mexico to the northwestern Costa Rican coastal plain, and from specimens reared from the Area de Conservacion Guanacaste, Costa Rica. The wasp larvae develop in the caterpillars of a relatively unrelated array of at least 24 species of pyrgine Hesperiidae. These hosts live in the broken shade and sun of forest edges while feeding on a variety of herbs, vines, and low woody plants. Oviposition occurs in an early to middle instar caterpillar, and a single wasp larva emerges from a penultimate or ultimate instar caterpillar to spin its large elongate white cocoon in the caterpillar’s shelter next to the empty skin and head capsule of the caterpillar. Bassus brooksi is distinctive in not attacking any grass-feeding Hesperiidae caterpillars (Hesperiinae) in this same habitat, and in apparently ignoring many species of sympatric pyrgine hesperiids as well as all other taxa of caterpillars. Bassus brooksi is closely related to Bassus spiracularis, which ranges over much of North America, is broadly sympatric with B. brooksi in northern Mexico, and has been reared only from pyrgine hesperiid caterpillars. These are the only two species of agathidine braconids known to attack butterfly larvae. It is hoped that publication of this information in a lepidopterological journal will stimulate the recording of these parasitoids when they are encountered while studying caterpillars.