Mating behavior of the alfalfa weevil, Hypera postica (Gyllenhal)

The qualitative and quantitative aspects of mating behavior, the stimulus for locating and mating, and the effects of varying temperatures on mating behavior and oviposition were studied in the laboratory.

Postdiapausing weevils, collected in April, and nondiapausing weevils, reared in the laboratory, were utilized. In both groups, the males aggressively mounted the females from any angle or position with little or no indication of prior courtship.

In petri dishes at 75 ± 3° F, both groups spent about 59% of their total time in mating behavior. Mounted time spent in actual copulation (aedeagus inserted) was 47% for nondiapausing pairs and 74% for postdiapausing pairs. This difference in behavior was probably caused by the younger, nondiapausing females which often prevented copulation by tucking the genital opening under the elytra. Males, when given a choice between virgin and non-virgin females, mated with non~virgins in a ratio of 7:1. Nondiapausing pairs mounted fewer times .for longer durations per mounting than the postdiapausing. Crowding by other weevils appeared to reduce mating efficiency, but not mating initiation.

Sight was found to play a role in attracting weevils to each other over distances of.a few inches. No evidence of sound production was discovered, nor was there found to be a pheromone serving as a sex attractant. Since males mounted other males as well as other species of curculionids, there is apparently rto mechanism for recognition of sex or species.

Higher temperatures resulted in a greater number of mountings of shorter duration. At lower temperatures, pairs mounted fewer times and riot infrequently copulated for as long as 12 hours. The number of ovipositing females and the average number of eggs per female increased with the temperature.