STRUCTURE AND FUNCTION OF THE CIBARIAL ARMATURE IN SIMULIIDAE

Cibarial armature morphology in adult female blackflies (Diptera: Simu liidae) is described using scanning electron microscopy. Three distinc t types of armature are recognized, comprising those with teeth, e.g. Simulium ochraceum, S.ornatum, S.veracruzanum and S.vorax; those with spicules, e.g. Austrosimulium bancrofti, S.damnosum, S.exiguum, S.meta llicum and S.neavei; and those lacking these projections, e.g. Prosimu lium rufipes and S.lineatum. Whereas the armature is poorly developed in vectors of human onchocerciasis such as S. damnosum, S. exiguum, S. metallicum and S. neavei, the well-developed armature in S. ochraceum , S. veracruzanum and S. vorax does not prevent these species becoming infected with Onchocerca spp. (Nematoda: Onchocercidae). Hence the ar mature is not primarily a mechanism to counteract microfilaria superin fection. Since cibarial armatures are more developed in the haematopha gous females than in the males of certain Families of flies, e.g. Cera topogonidae, Culicidae, Phlebotominae and Simuliidae in the sub-order Nematocera, evidently the armature has evolved in response to the bloo d-feeding habit. As the suction of imbibed blood by the cibarial pump may require a valve mechanism to prevent back-flow, it is suggested th at the armature is primarily for this purpose. Secondarily, the cibari al armature presents a damaging barrier against ingested microfilariae .