Some 1,881 Aedes aegypti (L.) progeny were reared as sibling samples taken from 196 families representing populations from 18 localities in South Africa, including anthropophilic and non-anthropophilic populations. The number of white scales on tergite I (T1) and in the basal band on tergite II (T2) were counted. Study of family samples showed that 60.2% of families were heterogeneous, containing both the type and formosus forms. Hence the division into nominate (type) and formosus subspecies is considered invalid. Multivariate statistical analysis of variance in the population samples in respect of T1 and T2 together showed that each population was significantly different from all others. However, statistical analysis of T1 and T2 alone showed that although some populations differed significantly, there was no consistent difference between anthropophilic and non-anthropophilic populations. It is concluded that in South Africa Ae. aegypti is a single polymorphic species displaying plasticity in its man-biting behavior.