Leaping behaviour and responses to moisture and sound in larvae of piophilid carrion flies

Observations suggesting that mature larvae of some carrion flies (Piophilidae) tend to leap off carcasses during rain motivated an investigation of the ontogeny and possible functions of larval leaping behaviour and larval responses to two stimuli associated with rain: moisture and sound. These behaviours were investigated in larvae of Prochyliza xanthostoma Walker (Diptera: Piophilidae) by means of laboratory-and field observations and experiments. Mature larvae left their feeding substrates (rotting meat) in response to either moisture or rattling sound. The response to moisture was exhibited also by immature larvae. Once on the carcass surface, however, only mature larvae leaped off and pupated in the surrounding soil. The response to sound and the ability to leap only appeared late in larval development and were lost in the prepupal stage. Because rain may facilitate larval locomotion on carcass surfaces, and leaping appears to represent a more rapid and efficient means of leaving a carcass than creeping, these responses may reduce the metabolic costs and predation risks experienced by mature larvae moving to pupation sites in the soil. Thus, the ability to leap and the responses to moisture and sound may represent ontogenetic adaptations associated with a brief stage of larval development.