A review is presented discussing the evolution, life cycle, taxonomy, diversity and malacophagous predation and parasitism of the marsh flies. It focuses on the effects of the Sciomyzidae as natural biological control agents in the dynamics of terrestrial Gastropoda population. Marsh flies are shown to meet the requirements of a successful biological control agent. It is concluded that these dipterans are significant factors in gastropod population dynamics and provide pest suppression without adverse effects on native nontarget species.
Host characteristics, hyperparasitism, larviposition behaviour and generation time of Sarcophaga penicillata Villeneuve a parasitoid of the conical snail, Cochlicella acuta Müller (Mollusca: Helicidae) in southern France are described. Only snails which aestivated on vegetation were found to be parasitized by S. penicillata. Sarcophaga penicillata preferred C. acuta which were both significantly higher off the ground and larger in size than the population averages. Of the 2768 snails collected at the study site, 4% (112) were parasitized by S. penicillata, of which 36.6% (41) failed to emerge while 34% (38) were hyperparasitized. The predominant hyperparasite was Novitzkyanus cryplogaster Bouček (Hymenoptera: Pteromalidae) which was responsible for 79% (30) of the hyperparasitism. Larvipositing S. penicillata were observed to fabricate a hole in the epiphragm of resting snails in which they deposited 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 superparasitism. 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. penicillata 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.
Abstract.
The oviposition behaviour of Simulium reptans L. is described from two sites on the River Spey, Scotland. Female aggregations were observed immediately downstream of oviposition sites and were composed mainly of gravid flies (range 60–80%0) together with smaller numbers that were either freshly bloodfed (range 2–17%) or infected with mermithid nematodes (range 0–30%).
The time from landing on the oviposition sites to the onset of oviposition was recorded. The time in the presence of greater than 1‐day‐old eggs did not significantly differ from sites with no eggs present. However, the presence of freshly laid or I‐day‐old eggs significantly shortened the time to onset of oviposition. The cues that elicit oviposition are unknown but it is speculated that they may involve a pheromone.
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