Responses of Nondiapausing Flesh Flies (Diptera: Sarcophagidae) to Low Rearing Temperatures: Developmental Rate, Cold Tolerance, and Glycerol Concentrations

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Abstract
The developmental rate of the flesh fly Sarcophaga crassipalpis Macquart reared under nondiapause conditions (L:D 15:9) shows a linear response to temperature between 15 and 30°C at all stages except the embryo. Temperatures above 20°C are essential for completion of embryonic development. Thermal constant threshold (T) in this species is 10.0-11.3°C (except embryo, where T = 16.9°C), and 369 degree-days above the threshold are required for completion of a single generation. Generation time is 50.6 d at 20°C and 21 d at 30°C (Ql0 = 2.4). The interval between departure from the larval food source and the onset of pharate adult development shows the greatest response to temperature change, indicating that physiological processes occurring at this time are especially sensitive to temperature regulation. Rearing temperature greatly influences cold tolerance—pharate adults (red-eye stage) reared at 15°C readily survive exposure to −10°C for 2 h while flies reared at 30°C cannot tolerate 1 h at − 10°C. Differences in cold hardiness at various rearing temperatures are correlated with the concentration of glycerol, the major cryoprotectant. Thus, even nondiapausing flesh flies can achieve a moderate level of cold hardiness when reared at low temperature.