Dispersal behavior of the southern pine beetle,Dendroctonus frontalisZimmermann (Coleoptera: Scolytidae), in response to synthetic aggregating pheromone (frontalin) indicates an exponential decrease in response with distance from the site of emergence. Differential response during dispersal among genotypes at a polymorphic esterase locus was found by using starch gel electrophoresis. These differences produced allelic distributions that predict increased genetic diversity concurrent with increasing dispersal distance from the source population.