During the course of their evolution,Ae. atropalpus andAe. epactius have undergone considerable genetic differentiation. The average genetic distance between the two species was 0.458 ±0.05. The average genetic distance between populations ofAe. atropalpus was 0.019 ± 0.01 while the average distance between populations ofAe. epactius was 0.075 ±0.02. The GREEN population, representing the new “form” ofatropalpus found breeding in discarded tires, exhibited electromorph frequencies characteristic of the “typical”atropalpus populations. Of the enzymatic loci examined, ADK2 was species diagnostic, and PGi was species discriminating. The electrophoretic results from the populations examined have provided additional support for the present taxonomic status of the two species.