Thermosensitivity and the acquisition of thermotolerance in eggs of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae)

Young (2-h-old) and mature (26-h-old) eggs of Queensland fruit fly, Bactrocera tryoni (Froggatt) were tested for development of thermotolerance by acclimatising them at a range of temperatures (30,35,37 and 40°C) for 1-6 h, then challenging them at 46°C for a time needed to achieve the LTso.Both young and mature eggs had the ability to develop thermotolerance and showed variable and differing responses, depending on the temperature and duration of acclimation. Young eggs acclimatised at 30°C for 3 h or 5 h or at 35°C for 6 h showed significantly decreased mortality (p sO.05) when challenged compared to controls held at 26°C, indicating development of thermotolerance. Mature eggs acclimatised at 35°C or 37 °C also showed significantly decreased mortality (p sO.05). When acclimatised at 40°C, both young and mature eggs showed higher mortality than controls. Mortality in mature eggs was significantly different (p sO.05) only after 6 h of acclimation, but mortality for young eggs was always greater (p sO.05) than controls.