Morphometric studies on Culex quinquefasciatus and Mansonia africana (Diptera: Culicidae) in Abeokuta, south-western Nigeria.

Some of the important mosquito species are generally sympatric in terms of their geographical distributions, and are difficult to identify based solely on examination of adult females using the available morphological keys. In this study, adult mosquitoes were collected indoors in Abeokuta in south-western Nigeria between August 2005 and July 2006 using Center for Disease Control light traps. The objective was to investigate possible morphological differences in populations of Culex quinquefasciatus and Mansonia africana. Six morphological characters namely, wing length, antennal length, proboscis length, foreleg length, mid leg length and hind leg length were measured in the two species. A total of 868 Cx quinquefasciatus and 962 M. africana were collected during the study period. The mean length was observed to be higher in most characters during the wet season than the dry season but the variation was not statistically significant (P > 0.005). In M. africana, the antennal length, proboscis length, foreleg length and midleg length showed one peak each. The wing length exhibited three peaks while hind leg length showed two peaks. For Cx quinquefasciatus, the antennal length, proboscis length, foreleg length, mid leg length and hind leg length indicated one peak. The wing length however showed three peaks. Each of the peaks observed in wing length and hind leg length of M. africana and wing length of Cx quinquefasciatus was assumed to be a specific population. The coefficient of differences (CDs) for each population indicated the presence of three populations in M. africana (CD > 1.28). However, the hind leg length showed that the two populations were the same (CD < 1.28). Three populations were also obtained from CD for wing leg length of Cx quinquefasciatus (CD > 1.28). Other characters indicated the presence of only one population. The results therefore underscore the need to investigate the status of the two species in relation to species complex.