Snails, slime and sciomyzid flies – prey location in a malacophagous Diptera

Abstract: The family Sciomyzidae is unique amongst insects in that almost all species areexclusively malacophagous. Globally, this feeding behaviour has made the family a target for theselection and assessment of biological control agents of snail intermediate hosts of trematodediseases and of gastropod pests of agriculture and horticulture. Although a wide range ofinformation has been published on the life history of these flies, relatively little is known aboutprey location mechanisms. In this study, the ability of neonate and third instar larvae of theaquatic sciomyzid, Sepedon spinipes, to follow fresh and aged (45 minutes) snail mucus trailswas assessed using filter paper Y-mazes. When fresh mucus trails were used, all of the neonatesand third instar larvae displayed a positive response and followed the mucus trail into theexperimental arm. The stimulatory substance(s), however, appeared to become inactive with timeand after 45 minutes none of the tested larvae reached the trail end. These results suggest thattrail-following behaviour in Sciomyzidae is an innate response and that aquatic species may alsohave the potential to forage for snails on shoreline and semi-aquatic areas.