The ability of Anopheles gambiae complex mosquitoes to transmit Plasmodium infection is known to be variable within sibling species of the complex with strains that cannot transmit the parasite. High sporozoite infection rate recorded showed that A. gambiae mosquitoes are potent malaria vectors in southwestern Nigeria. The aim of this study was to identify the infective and refractory strains of A. gambiae mosquitoes and to determine the sporozoite infection rate in this area. The infective strains were A. gambiae (sensu stricto) and A. arabiensis, while the refractory strains were A. gambiae (sensu stricto). However, ovarian polytene chromosome banding patterns could not be used to distinguish between the infective and refractory strains of A. gambiae (sensu stricto). This study showed that the refractory strains of Anopheles gambiae complex are present, but in low frequencies, in southwestern Nigeria, and that the sibling species of Anopheles gambiae (A. gambiae s.s. and A. arabiensis) are potent malaria vectors.

Laboratory studies were conducted on three Drosphila species and another drosophilid, Zaprionus vittiger Coquillet as well as on a phorid, Megaselia scalaris Loew, all of which share similar ecological niche. Temperature treatments revealed varying degree of temperature tolerance while nutritional stress produced a reduction in body size and a lengthening of larval developmental period in all but one of the species. Further laboratory tests are being carried out to isolate nutritional and temperature sensitive mutants for use in gene combinations that could be employed in genetic programme for insect control .