SHORT-RANGE DISPERSAL OF MASS-REARED DIACHASMIMORPHA-LONGICAUDATA AND D-TRYONI (HYMENOPTERA, BRACONIDAE), PARASITOIDS IN TEPHRITID FRUIT-FLIES

Cohorts of two species of mass-reared opiine braconid parasitoids Diachasmimorpha longicaudata (Ashmead) and D. tryoni (Cameron) were released at two study sites (a mature guava orchard and a large grass field) to study their height of dispersal in the vertical plane and their direction of dispersal in the horizontal plane. A higher percentage of released parasitoids of both sexes and both species was recaptured in the orchard than was recaptured in the grass field. Highest recovery in the orchard canopy for both species coincided with the fruit abscission period. Movement in the vertical plane followed an approximately normal distribution in the grass field, with a mean recapture height of 133.3 cm (+/-1.9). In the orchard, vertical distribution was negatively skewed with a mean recapture height of 153.9 cm (+/-1.1). In the orchard, the median height of dispersal of females of both species rose to >200 cm during the period of fruit abscission in the canopy and fell to <100 cm after most of the fruit had fallen. In the horizontal plane, the mean direction of dispersal in both vegetation types was toward the southwest, presumably in response to prevailing northeasterly trade winds. The relevance of the results to augmentative biological control of tephritid fruit flies in Hawaii is discussed.