AbstractThe aphid genusCrypromyzuswas studied using starch. el electrophoresis in order to establish differences between the various taxa and to estimate their paylogenetic relationships. A low degree of polymorphism and heterozyosity was observed. Taxa previously assumed to be homogeneous appeared to consist of different tost‐secific forms. Polymorphism at the PGI locus was used to assess the degree of isolation. It was founf to range from complete separation to a reduction in gene flow. Three methods of estimating hylogenetic relationships were employed: the UPGMA clustering method using Nei'sgenetic distance; the Rogersdistance together with the distance Wagnermethod and the independent allele model of Mickevichand Mitter(1981) combined with the Wagnerparsimony method. The results of all three methods agree that several of the taxa are closely related but assign different lower branching points to the phylogenetic tree. The independent allele model is discussed in more detail because it is not often applie