Development and Field Evaluation of a Novel, Inexpensive Passive Trap for Monitoring Dispersal of Necrophagous Dipteran Larvae

Techniques for the survey of necrophagous dipterans are frequently designed for adult flies and often neglect forensically important information, such as the postfeeding larval dispersal following carcass colonization. In this study, we propose and test a novel trap design for the collection of dipteran larvae at the postfeeding stage. The Trap for Dispersing Larvae (TDL) consists of two semiindependent parts: 1) a 2-liter PET bottle, containing the attractant (carcass); and 2) a plastic box, which selectively captures postfeeding dispersing larvae. Based on a field test in a dry forest fragment in Brazil, the TDL trap captured ca. 1,500 larvae of 13 species of Calliphoridae, Muscidae, Fanniidae, and Sarcophagidae. The species richness of dispersing larvae recorded in our study was ca. 60% of that previously recorded in this area. As the TDL trap can assess larval dispersal without interfering with carcass decomposition, we demonstrate that it can be used to assess temporal variation in the dynamics of colonization. In the present study, most larval dispersal occurred at 5-d postexposure, but the traps remained efficient until 7 d, by which time rat carcasses had skeletonized. We conclude that the TDL trap captures the dispersing dipteran larvae with little interference in carcass decomposition processes. The trap also provides a representative sample of species and is simple to use and of low cost.