Diapausing larvae of the midge Aphidoletes aphidimyza (Diptera : Cecidomyiidae) survive at subzero temperatures in a supercooled state but tolerate freezing if inoculated by external ice

Diapausing larvae of Aphidoletes aphidimyza (Diptera: Cecidomyiidae) had re latively low supercooling points (SCP) ranging from -19.0 to -26.4 degreesC . None of the specimens that froze at this temperature survived. A high sur vival rate (up to 87%) at -10 degreesC for 10 days was observed in supercoo led larvae. Such features are characteristic for insects that use a chill-t olerance strategy of cold hardiness. However, the cocoons formed by the dia pausing larvae were penetrable by external ice crystals and the larvae show ed a relatively high survival rate (23 - 34%) at -10 degreesC for 10 days a lso in the frozen state caused by inoculation by external ice at high subze ro temperatures. Such a duality with respect to cold hardiness strategies s eems to be ecologically relevant to overwintering in soil habitats where th ere may be unpredictable contact with external ice.