Biological control of pestiferous slugs using Tetanocera elata (Fabricius) (Diptera: Sciomyzidae): Larval behavior and feeding on slugs exposed to Phasmarhabditis hermaphrodita (Schneider, 1859)

While the larval stage of Tetanocera elata (Diptera: Sciomyzidae) is a known parasitoid and predator of pestiferous slugs, its biology and predatory behavior as well as its interaction with slug parasitic nematodes requires further investigation. In this study, survival of larvae fed from the neonate stage on Deroceras reticulatum Müller (a previously known prey species) was significantly greater (P = 0.023) than for larvae fed on Deroceras invadens Reise with 100% and 40% survival respectively. However, when fed solely on D. reticulatum which were previously exposed to P. hermaphrodita, only 20% of neonate larvae pupariated successfully. Ninety percent of neonate larvae maintained without food for the first four days and subsequently fed on D. reticulatum pupariated successfully although this decreased to below 50% for ≥6 days without food. Predatory third instar T. elata larvae appeared to select nematode-exposed D. reticulatum over non-exposed slugs with the continued feeding on nematode-exposed slugs also reducing the chances of successful pupariation by 25%. Records of maximum egg-laying by laboratory-reared female adults were greater (487 eggs) than previously recorded for field-caught adults (3 7 3). The implications of these results for the potential use of T. elata as a biological control agent of pestiferous slugs are discussed.