Taxonomic value of spermatheca size for distinguishing four members of the Anopheles gambiae complex in East Africa.

Measurements of spermatheca diameter and wing length were made on 8 East African mosquito populations comprising Anopheles merus and A. gambiae species A, species B, and the "Bwamba cytotype" (=species D). The results showed that, on average, the spermatheca in species A females is larger than in species B. In each of two Tanzanian localities harbouring sympatric populations of A and B an overlap of 20% was observed between the frequency distributions of spermatheca diameter in this pair of species. In the Bwamba cytotype, spermatheca size resembled that of species A but the wings were longer than in all other populations investigated. A. merus females had a small spermatheca enabling about 50% of individuals to be distinguished from species A and about 30% to be distinguished from species B. The correlation coefficient between the two measurements was positive but low. It was concluded that no taxonomic advantage exists in combining both these features for classifying individual mosquitos. With multiple samples, however, the relationship of mean wing length to mean spermatheca diameter appeared to be characteristic for each member of the complex. It is concluded that with these East African populations of the A. gambiae complex, the measurement of spermatheca size has little value for distinguishing between individual females of the different sibling species.