Insects that are psychrotrophic can survive cold temperatures through several general mechanisms (unlike opportunistic and chill susceptible insects): (1) chill tolerance, (2) freeze avoidance, and (3) freeze tolerance. Chill tolerant insects succumb to freezing temperatures after prolonged exposure to mild or moderate freezing temperatures. Freeze avoiding insects can survive extended periods of time at sub-freezing temperatures in a supercooled state, but die at their supercooling point. Freeze tolerant insects can survive ice crystal formation within their body at sub-freezing temperatures. Freeze tolerance within insects is argued to be on a continuum, with some insect species exhibiting partial (e.g., Tipula paludosa, Hemideina thoracica
), moderate (e.g., Cryptocercus punctulatus), and strong freezing tolerance (e.g., Eurosta solidaginis and Syrphus ribesii), and other insect species exhibiting freezing tolerance with low supercooling point (e.g., Pytho deplanatus).