Canopy distribution and microclimate preferences of sterile and wild Queensland fruit flies

Abstract

Insects tend to live within well-defned habitats, and at smaller scales can have distinct microhabitat preferences. These preferences are important, but often overlooked, in applications of the sterile insect technique. Diferent microhabitat preferences of sterile and wild insects may refect diferences in environmental tolerance and may lead to spatial separation in the feld, both of which may reduce the control program efciency. In this study, we compared the diurnal microhabitat distributions of mass-reared (fertile and sterile) and wild Queensland fruit fies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae). Flies were individually tagged and released into feld cages containing citrus trees. We recorded their locations in the canopies (height from ground, distance from canopy center), behavior (resting, grooming, walking, feeding), and the abiotic conditions on occupied leaves (temperature, humidity, light intensity) throughout the day. Flies from all groups moved lower in the canopy when temperature and light intensity were high, and humidity was low; lower canopy regions provided shelter from these conditions. Fertile and sterile mass-reared fies of both sexes were generally lower in the canopies than wild fies. Flies generally fed from the top sides of leaves that were lower in the canopy, suggesting food sources in these locations. Our observations suggest that mass-reared and wild B. tryoni occupy diferent locations in tree canopies, which could indicate diferent tolerances to environmental extremes and may result in spatial separation of sterile and wild fies when assessed at a landscape scale.