REVUE SUISSE DE ZOOLOGIE 110 (4): 817-832; décembre 2003 Predation by larvae of Sepedon ruficeps (Diptera: Sciomyzidae) and population dynamics of the adult flies and their freshwater prey Louis Ghélus GBEDJISSI!, Jean-Claude VALA2, Lloyd KNUTSON? & Christian DOSSOU! Université Abomey-Calavi, Box 526, Cotonou, Republic of Benin. E-mail: gbedjiss@syfed.bj.refer.org 2 Université d'Orléans, Laboratoire de biologie des Ligneux et des Grandes Cultures, UPRES EA 2107, BP 6759, 45067 Orléans Cedex 2, France. E-mail: jean-claude.vala@univ-orleans.fr 3 Salita degli Albito 29, 04024 Gaeta, (LT), Italy. E-mail: Ivknutson @tiscali.it Predation by larvae of Sepedon ruficeps (Diptera: Sciomyzidae) and population dynamics of the adult flies and their freshwater prey. - The biology, phenology, and population dynamics of the adults of Sepedon rufi- ceps, the most widely distributed species of Sciomyzidae in Africa, were studied in Benin in permanent and temporary freshwater habitats. The feeding behavior of the larvae, expressed as the number of snails consumed, varies as a function of the species of prey utilized (Bulinus forskalii or Biomphalaria pfeifferi), as a function of the sizes of the predator/prey, and as a function of the stages of development of the larvae. In relation to the snail-prey, the second- and third instar- larvae show a food choice varying according to the specific ethology of the prey attacked. In all cases, the third- instar larvae always consume the largest number of snails and indif- ferently attack all of the species of snails utilized in laboratory rearings. The larvae consume, equally well, B. forskalii that are healthy or parasitized by the larvae of trematodes. Curiously, in laboratory rearings, in the absence of snails, the larvae of S. ruficeps are equally capable of attacking and devel- oping at the expense of Aulophorus furcatus, a small, freshwater, oligo- chaete annelid (Naididae). Key-words: Diptera - Sciomyzidae - Sepedon ruficeps - predation - pheno- logy - biology - freshwater snails - Oligochaeta. INTRODUCTION Since the publication by Berg (1953), Sciomyzid flies have been well known for the obligate malacophagous feeding of their larva. Throughout the world, 517 species have been described, of which 64 are from the Afrotropical Region. In this Region, 49 Manuscriptaccepted20.06.2003