| I compared the performance of different traps, and the effect of trap placement, in attracting blueberry maggot flies, Rhagoletis mendax Curran, of different reproductive maturity stages and sex. Irrespective of maturity status or sex, captures of flies on red or green spheres were better than on Pherocon AM traps. Captures of flies at different positions depended on bush size, but were also not dependent on maturity status or sex. The use of traps allowed the determination that the flight period of blueberry maggot fly, in New Jersey, was much longer than previously thought, extending from early June to early November. Populations with distinct phenology were characterized, one emerging in June--July, and the other in September, present in commercial blueberry fields. I studied the overwintering development of both populations by taking samples from outdoors at constant intervals, and verified distinct temperature-development relationships throughout the season in the late population. Emergence models predicted emergence of the early population with a four-day accuracy, but were unable to forecast emergence of the late population because of a slowdown of development in summer. Although a larger number of pupae of the late population emerged without diapause, this trait is not involved in the timing of emergence in the field. Early and late populations of the blueberry maggot differ in postdiapause development rates, and, in the case of the late population, the possible occurrence of delayed development in summer. The taxonomic status of late populations was evaluated using allozyme markers. Frequencies at one locus depart from what is found throughout the range of the blueberry maggot. I compared sympatric populations in a wild area, and found consistent differences, in two years. Exposure of pupae to selective pressures on their life cycle did not lead to any response at the locus displaying allele frequency differences. Populations in a wild area late in the season were genetically similar to those found in commercial blueberry fields. Together, phenological and genetic differences indicated the presence of two distinct populations. Phenological and genetic data also suggest early emergence might be the derived character in the evolution of the blueberry maggot fly. |
