Cold hardiness of some adult mosquitoes in central Alberta

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Abstract
Temperatures were recorded continuously in overwintering sites of female Anopheles earlei Vargas, Culex territans Walker, and Culiseta alaskaensis (Ludlow) near George Lake (53°57′N, 114°06′W). Daily mean and absolute minimum temperatures in winter (November–March) 1972–75 were −6 and −31 °C in three rock piles, −6 and −21 °C in a log pile, −2 and −7 °C in a mammal burrow, and −10 and −42 °C in the open air. Live An. earlei and Cx. territans from rock piles in winter had mean supercooling points of −23.6 and −26.1 °C respectively. Freezing to determine supercooling points was fatal to all mosquitoes tested. Culex territans females collected in fall (September–October) had a mean supercooling point of −20.1 °C and an LT50 (median lethal time) of 138 days at −5 °C. Female Cs. inornata (Williston) were not found in winter; those collected in fall had a mean supercooling point of −11.3 °C and LT50 of 20 days at −5 °C. Supercooling points of Cs. inornata females laboratory reared at 20 °C were lowered after 1 or 10 days at 10 °C, but not at 2 °C, and not affected by blood or meconium in the midgut. Laboratory-reared, diapausing Cs. alaskaensis females had a mean supercooling point of −12.9 °C and an LT50 of 30 days at −5 °C. Nondiapausing Cs. inornata females had a mean supercooling point of −14.4 °C but their LT50 was only 9.3 days at −5 °C.

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