Survival Rates of the Queensland Fruit-Fly, Dacus-Tryoni, in Early Spring - Field-Cage Studies With Cold-Acclimated Wild Flies and Irradiated, Warm-Acclimated or Cold-Acclimated, Laboratory Flies

Abstract

During spring in 1976, 1977 and 1978, field-cage studies were undertaken 80 km SSW. of Sydney. These examined the relative survival abilities of irradiated Dacus tryoni, that had been conditioned either to warm or to cold prior to release, and of wild flies cold-conditioned to post-winter temperatures. In 1976, survival rate of warm-conditioned steriles was compared with that of wild flies. The former suffered higher mortality than the latter, and this was thought to be because of their inability to with- stand frosts. In 1977, a comparison was made between cold-conditioned irradiated flies and wild flies. There was no statistical difference in survival rate but both fly types suffered substantial mortality caused by successive extreme minima, lack of rain and, latterly, high daytime temperatures. A simultaneous comparison of both kinds of sterile fly and wild flies in 1978 showed that cold-conditioned steriles survived better than warm-conditioned ones during the initial weeks, when the cold-torpor thresholds of the two types remained distinct; survival of cold-conditioned steriles was similar to that of the wild flies.