Background & objectives: The ecology and distribution of various mosquito species is important in the determination of mosquito vector abundance and associated diseases prevalence. The distribution of various mosquito genera in natural and artificial habitats and their relative species abundance was studied between August 2002 and July 2003 in three foci (Uromi, Ekpoma and Auchi) comprising the Esan and Etsako regions of Midwestern Nigeria.

Methods: Sampling was carried out by the method of Hopkins (1952) by dipping using a pipette or ladle depending on container types. Pooled contents of smaller containers were sampled with a pond net. All breeding sources of mosquito larvae were grouped into five (5) depending on their nature, constitution and the physiochemical properties. Artificial mosquito cultures were also carried out in four different container types; plastics, metal cans, earthenware pots and bamboo strips, in parts of two different macro habitats subdivided into area of high human activities (AHHA) and areas of derived/secondary vegetation (ADSV). Environmental temperatures, rainfall and relative humidity were monitored during the study.

Results: The present study revealed 17 mosquito species belonging to three genera (Anopheles, Culex andAedes) which are potential vectors of four human diseases in the areas surveyed. A total of 736 mosquito larvae were encountered in artificial sources and 568 larvae were harvested from natural sources. Pools, plastics and metal cans were the predominant artificial sources of mosquito larvae.

Conclusion: The contribution of human activities and increasing environmental modification to the breeding of human disease vector mosquitoes is of importance and selective vector control measures including larviciding are recommended particularly before onset of rainy season.