Biology of Slug-Killing Tetanocera (Diptera: Sciomyzidae)1

Abstract

Information is presented on the life cycle and feeding habits of larvae of 3 Nearctic species of slug-killing Tetanocera. T. plebeia (Loew) and T. valida (Loew) are host specific as newly hatched larvae for Deroceras laeve (Müller) and D. reticulatum (Müller) slugs. The young larvae of T. plebeia remain for several days under the mantle of the host, where they apparently feed on proteinaceous secretions. The older larvae are overt predators of terrestrial gastropods and utilize a paralyzing neurotoxin. The lst-stage larvae of T. valida invade the invaginated eye tentacles of their hosts and remain in place until the 3rd instar is attained. They then become predaceous, but in contrast to those of T. plebeia, the older larvae of T. valida invade the mouth of their Deroceras prey and usually do not cause death until 8–24 hours later. All 3 instars of T. clara Loew are restricted to Pallifera and small Philomycus. The newly hatched larvae invade the mouth of the host, where they remain until the 3rd instar. Like those of T. valida, the older larvae of T. clara are predaceous and invade the mouth of their prey. They do not kill the slug until several hours later. All 3 species consume between 2 and 8 slugs during the 20–30 days of larval life. Puparia are formed in surface litter. All 3 species are multivoltine and overwinter as pupae in diapause.