Ant-Attended Nymphal Aggregations in the Enchenopa binotata Complex (Homoptera: Membracidae)

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Abstract
Females of Enchenopa binotata Say deposit eggs under the bark of branches and cover them with a white secretion (egg froth). Egg froth contains an ovipositional attractant which attracts females to branches that already have egg masses present. After oviposition is completed, egg masses are highly clumped on branches within the host plant. Aggregations of nymphs are formed when eggs hatch the following spring, with group size influencing ant attendance and nymphal survival. Survival of nymphs varies among trees due to variation in attendance by ants. I postulate that variation among individual trees in nymphal survival and ant attendance promotes disjunct insect distributions. Such distributions magnify microgeographic distances among insect populations on conspecific host plants as well as those on other host plant species. Such factors contribute to molding insect genotypic variation to a host plant species, and have facilitated the divergence of E. binotata into a complex of reproductively isolated species, one on each species of host plant.