HOST DISTRIBUTION, LARVIPOSITION BEHAVIOR AND GENERATION TIME OF SARCOPHAGA-PENICILLATA (DIPTERA, SARCOPHAGIDAE), A PARASITOID OF CONICAL SNAILS

Host characteristics, hyperparasitism, larviposition behaviour and gen eration time of Sarcophaga penicillata Villeneuve a parasitoid of the conical snail, Cochlicella acuta Muller (Mollusca:Helicidae) in southe rn France are described. Only snails which aestivated on vegetation we re found to be parasitized by S. penicillata. Sarcophaga penicillata p referred C. acuta which were both significantly higher off the ground and larger in size than the population averages. Of the 2768 snails co llected at the study site, 4% (112) were parasitized by S. penicillata , of which 36.6% (41) failed to emerge while 34% (38) were hyperparasi tized. The predominant hyperparasite was Novitzkyanus cryptogaster Bou cek (Hymenoptera: Pteromalidae) which was responsible for 79% (30) of the hyperparasitism. Larvipositing S. penicillata were observed to fab ricate a hole in the epiphragm of resting snails in which they deposit ed one larva. After larviposition, female S. penicillata remained with the freshly parasitized snail a mean time +/- SE of 25.2 +/- 10.3 min . It is suggested that this may be an adaptive response to avoid super parasitism, The mean generation time of S. penicillata when reared in the laboratory was 18 days, indicating that more than six generations are possible during summer in the south of France. During winter, S. p enicillata enters diapause in the pupal stage within a host snail for up to 6 months. The possible utility of S. penicillata as a biological control agent of introduced conical snails is discussed.