Comparative Study of Eastern and Western North American Populations of Hippodamia convergens (Coleoptera: Coccinellidae)

Hippodamia convergens is a widely distributed insect predator in the United States and parts of Canada and Mexico. Several insectaries and companies collect the overwintering adults from aggregation sites in the Sierra Nevada Mountains in California during their winter dormancy. Collected beetles are then sold to farmers and home growers in the United States for augmentative biological control. This practice could have negative impacts on local populations of Hippodamia convergens in the Eastern United States. Intra-specific variation among H. convergens populations was examined for two characteristics of adults: the presence of endosymbiont bacteria and photoperiod inducing diapause. Preliminary results indicate the presence of endosymbiont bacteria in two Western United States populations of H. convergens. Considerable variation in the critical photoperiod for diapause induction among four populations of H. convergens has been observed. Additional studies are required to determine if this intra-specific variation is being influenced by augmentative releases of H. convergens.