Effects of cold-acclimation on supercooling and survival of the rusty grain beetle, Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae), at subzero temperatures

The survival of non-acclimated adults and large larvae (third and fourth instar) of Cryptolestes ferrugineus (Stephens) was found to be greater than that of pupae, small larvae (first instar), and eggs at −12°, −6°, and 2 °C. The effect of acclimation on adult survival at subfreezing temperatures was determined. Different degrees of acclimation were achieved by exposing adults for different periods of time at 15 °C. At −6° and −12 °C adult survival increased as the time of acclimation increased. The LT50 of acclimated adults increased as much as nine times at − 6 °C and 56 times at −12 °C compared to the LT50 of non-acclimated adults. The supercooling point of adults was lowered from −16.5 °C for non-acclimated adults to − 20 °C for adults acclimated at 15 °C and to −21 °C for adults acclimated at 15° and then 4 °C. It is suggested that C. ferrugineus is able to survive the winter in unheated granaries in the Prairie Provinces mainly because of its ability to acclimate to low temperatures.