International Journal of Comparative Psychology

Molecular genetics studies on the chymomyzids have produced divergent results on their relation to the genus Drosophila . Behavior has been used to assess the appropriateness of their inclusion in the genus (Maclntyre and Collier, 1986) or off the drosophilid main stem (Beverley and Wilson, 1984). Laboratory and natural population studies on Chymuniyza amoena in Michigan and Virginia and observations on multiple species aggregations at natural sites in 1986 and 1987 in Virginia's Allegheny Mountains have been carried out. Wing-waving and foreleg splaying are characteristics of both sexes. In nature, females do not approach males until sexually mature. All population sizes seem small. Studies on C. amoena indicate that behavioral phenotypic plasticity exists for all stages: lanal feeding substrates, pupation site choice, mating system, egg deposition and oviposition site selection. Behavioral traits shared with the lek Drosophila (Hawaiian and Australian), genus Scaptomyza , subgenus Scaptodrosophila , subgenus Sophophora and genua Lissocepha Ia among the drosophilids, and the tephritids, otitids and hyinenopterans outside the family Drosophilidae suggest that chymomyzids retain characteristics of primitive drosophilids that have undergone selective modification in the evolution of different drosophilid lineages. Significant differences in aggression between Michigan and Virginia C. amoena populations support this conclusion. Throckmorton (1962, 1966) anticipated the chymomyzid relation to the drosophilid stem from external and internal anatomical studies. A wood breeding habitat of most forest chymomyzids is also in agreement with recent molecular genetics evidence that fermented fruit breeding evolved later in drosophilid evolution.