Predatory Activity of Psychoda alternata Say (Diptera: Psychodidae) Larvae on Biomphalaria glabrata and Lymnaea natalensis Snails and the Free- Living Larval Stages of Schistosoma mansoni

Abstract

2 Abstract: Larvae of Psychoda alternata Say (drain fly) proved experimentally to have different degrees of predatory activity on egg masses of Biomphalaria glabrata Say, and Lymnaea natalensis Kruss, the snail hosts of Schistosoma mansoni and Fasciola gigantica in Egypt respectively. The larvae spoiled and consumed considerable numbers of egg masses and consequently reduced the rate of hatching. Large larvae (4 instar) destruct also newly hatched B. glabrata snails (< 3mm). The th consumption of Lymnaea egg masses by larvae was lower than in the case of B. glabrata probably due to the thicker gelatinous material surrounding the eggs. P. alternata larvae were found also to consume S. mansoni miracidia and cercariae and their presence during miracidial exposure of snails reduced markedly the infection rate of B. glabrata snails with Schistosoma and considerably decreased the total periodic cercarial production of infected snails. Therefore P. alternata larvae may play an important role in reducing the population density of medically important snails, free- living larval stages of S. mansoni and the schistosome infection of target snail with this parasite. Consequently P. alternata may be useful in the control of schistosomiasis transmission in aquatic habitats.