Thermal Responses of Oriental Fruit Fly (Diptera: Tephritidae) Late Third Instars: Mortality, Puparial Morphology, and Adult Emergence

Responses of late third instars of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), to high temperatures (43, 46, and 48°C) were investigated. The different heat exposures not only affected the timing of death but also induced different quantities of malformed puparia and changed the average eclosion time. A majority of larvae died immediately (as larvae) after 30 min at 46°C and ≥15 min at 48°C, whereas most individuals died as pupae after 10–25 min of 46°C, 5–10 min of 48°C, and 40–60 min of 43°C treatments. Lethal times estimated by immediate mortality were longer than those estimated by delayed mortality at the same high temperature. Surviving larvae formed four types of puparial morphology (normal, bottlenose, larviform, and peanut form). The percentage of normal puparia showed a negative correlation with exposure time at all test temperatures. The number of bottlenose was more than the larviform and the peanut at 46°C for ≤20 min and at 48°C for ≤10 min, respectively, whereas the number of larviform was more than the bottlenose and the peanut at 46°C and 48°C for longer exposure times. The average eclosion time increased at first, then decreased as the exposure time prolonged, and the longest average eclosion time occurred in the 40-min exposure at 43°C, 15-min exposure at 46°C, and 10-min exposure at 48°C.