Remarkably, tiny insects survive weeks and months of sub-zero cold each year. This post provides brief descriptions of how three common bugs manage this; Woollybear Caterpillars, Mosquitos, and Ticks.
Woollybear Caterpillar (Pyrrharctia isabella)
The woollybear hatches in the fall and overwinters in its caterpillar form, when it nearly freezes solid. Their bodies produce glycerol, a fluid that acts like antifreeze to product their organs from being damaged by freezing. Woollybears thaw in the spring and metamorphose into the Isabella Tiger Moth. To compensate for short growing seasons, the closely related arctic woollybear lives through several winters before changing into the moth.
Mosquitos (Order Diptera, Family Culicidae)
There are 51 species of mosquito in Minnesota, ~24 of them bite humans. Winter survival strategy varies among the species, but most survive as eggs laid in soil. These eggs enter a dormant state known as diapause in response to colder temperatures and shorter days. Eggs in diapause do not hatch until environmental signals are detected, like increased temperature or increased moisture. Typically a consistent temperature above 50 degrees Fahrenheit is needed before mosquito eggs hatch.
Ticks (Family Ixodidae)
There are about a dozen species of ticks in Minnesota, the two that are most common and of concern as disease carriers are the American dog tick or wood tick (Dermacentor variabilis) and the black-legged tick or deer tick (Ixodes scapularis). Ticks have eight legs, and so are actually arachnids (like spiders), not insects.
These Minnesotan ticks are quite resilient to cold temperatures. The American dog tick is typically not active below 45 degF, but the black-legged tick is quite active as long as temperatures are above freezing. Both ticks survive the coldest temperatures by staying beneath cover, like leaves, near to the ground. Even in bitter cold snaps, near the ground temperatures are usually warm enough for these ticks to survive.
American dog ticks are carriers of Rocky Mountain spotted fever, while the smaller black-legged ticks are the main carrier of Lyme disease. Transmission of disease typically requires the tick to have been attached for more than a day. Frequent checking for ticks is recommended to help people avoid these diseases.
Ticks position themselves at the tips of low-lying grasses and bushes, waiting to grab onto passing animals or people. So, their “landing spot” is usually near ground level. They crawl up to find an exposed spot to attach. Therefore, use of a repellent like permethrin on shoes, socks, and pant legs can be an effective guard against ticks.