SEASONAL DEVELOPMENT, BEHAVIOR, AND HOST SYNCHRONY OF DACNUSA DRYAS (NIXON) (HYMENOPTERA: BRACONIDAE) PARASITIZING THE ALFALFA BLOTCH LEAFMINER, AGROMYZA FRONTELLA (RONDANI) (DIPTERA: AGROMYZIDAE)

Abstract

AbstractStudies in eastern Ontario showed that the exotic parasite Dacnusa dryas (Nixon) typically has three generations a year that correspond seasonally to those of its host, the alfalfa blotch leafminer, Agromyza frontella (Rondani). The mature larvae of the third generation enter diapause in September and resume development in the spring. The egg – first instar interval, which occurs within the actively feeding leafminer, developed at rates similar to those of the host larva. The remaining two instars and the pupa, which occur within the host puparium, developed at rates similar to those of the host pupa; in the two non-diapausing generations, the durations of these stages decreased with rise in temperature from 13 to 23 °C. Coincidence of wasp flight and hatch of leafminer eggs was high in all three generations. This host–parasite synchrony results mainly from a sequence of three events during their life cycles: lack of development of the parasite beyond the first instar within the host larva, a temperature-dependent rate of development of the subsequent stages which is similar to that of the host pupa, and different overwintering strategies which result in the parasite emerging later than its host to sustain the relationship. Behavior of the parasite is described in relation to host detection, egg deposition, and reproduction.