Oviposition by two species of Drosophila (Diptera: Drosophilidae): behavioral responses to resource distribution and competition

We compared ovipositional patch selection by two species, Drosophila melanogaster Meigen and Drosophila simulans Sturtevant, alone and together, in 12-liter and 190-liter containers and with varied distributions of ovipositional patches (even, random, and clumped). D. simulans deposited significantly more eggs than D. melanogaster . Both species produced more eggs per female in the competitive situation than when alone. When the two species were together, they tended to avoid the same patches, thus avoiding interspecific competition. In patches containing the eggs of both species, D. melanogaster laid a greater proportion of eggs on the edge and D. simulans laid a greater proportion of eggs on the center; thus, the two species tended to avoid each other within sites. The distribution of eggs was best explained by assuming gregarious oviposition; females were clumped together, and egg production followed a logarithmic distribution.