Abstract
Mating ability and mating competitiveness were compared between mass-reared and wild strains of the melon fly, Dacus cucurbitae COQUILLETT. Mass-reared (L-) strain originated from the culture maintained for about 33-41 generations under artificial rearing conditions in the Mass-rearing Facilities in Ishigaki Is. Wild (W-) strain was collected from infested fruit, or was caught by a cue-lure trap in the field. When a pair of male and female flies were confined in a cage (30×30×45cm), the percentage of mated pairs was larger in L-strain than in W-strain. Supply of some pieces of sliced pumpkin in the cage increased mating ability of W-strain. In the four experiments, in which three different combinations of flies such as (1) W-female, W-male, L-male, (2) L-female, W-male, L-male, (3) W-male, W-female, L-female, (4) L-male, W-female, L-female, were confined in a cage, L-male×L-female pair mair mated most frequently, and W-male×W-female pair mated infrequently. In the experiments using larger cages (180×180×180cm) or when the smaller density of flies per cage was lower, mating competitiveness of W-males increased and that of L-males decreased. These results suggest that L-strain is adapted to artificial diet and narrow space under massrearing conditions. It was concluded that the evaluation of mating-competitiveness of the mass-reared sterile males in the small-cage experiments can not give a precise indication of the competitiveness under field conditions.
