Effects of Prolonged Freezing and Supercooling on Body Composition, Pupariation, and Adult Emergence ofEurosta solidaginis(Diptera: Tephritidae)

Abstract

Freeze tolerance and enhanced supercooling ability (freeze avoidance) are distinct adaptations in insects facilitating survival of subfreezing temperatures. It has been suggested that freeze tolerance has advantages over freeze avoidance with respect to certain aspects of insect ecophysiology. Third instars of the gall fly Eurosta solidaginis Fitch were kept either frozen or supercooled at −5°C for 10 wk. Supercooled larvae lost 26% of their wet weight and frozen larvae lost 14% of wet weight, mostly as a result of water loss during the treatments. Moreover, although supercooled larvae lost more water than did frozen larvae, lipid content was stable throughout both treatments. Freeze-treated larvae were 50% more likely than supercool-exposed larvae to survive to pupariation and adult emergence. E. solidaginis larvae survived prolonged freezing better than they endured prolonged supercooling, but it remains to be clarified whether or not this effect can be attributed to differences in water retention.