Insects of winter

One of the absolute joys of winter is the absence of biting mosquitoes and black flies, stinging wasps, and gardening banes such as aphids. With the exception of a few insects, such as some dragonflies and butterflies, very few insects migrate to escape the cold. Insects survive the winter using one of tow strategies: dormant or active overwintering.

Dormant overwintering

SnowScoripionfly.jpgMost insects wait out the winter by hiding out in a cozy little space under some bark or in the soil until spring sunshine and longer days signal them to emerge. One way to do this is as an adult. A lot of beetles use this strategy. Whirligig beetles, for example, can be found in the warmer months, spinning dizzily on the surfaces of ponds as they swarm in groups in their search for food. As winter threatens, they climb onto the shore, burrow under the leaf litter, and wait for their pond to thaw again. Blow flies (commonly called "house flies") also lay low as adults; to our annoyance, they often do so in our homes, resulting in a buzz of activity on our windows on sunny, winter days.

Other insects overwinter as pupae. the intermediate stage preceding adulthood, or as larvae. Giant silkworm moths, such as the large luna and polyphemus moths, remain as pupae, bundled up in fist-sized cocoons in the woods. Some moths survive as larvae (caterpillars). Most horse flies and deer flies live under water during their larval stage.

Finally, some insects leave their eggs behind to tough out the weather. Many bugs lay eggs in the summer, and the eggs do not hatch until the following spring. (To biologists, the true bugs are a distinct group of insects including aphids, cicadas and treehoppers.)

Active overwintering

A few insects do not avoid the cold weather, but actually remain active while snow (or freezing rain) blankets the land. Many aquatic insects, such as predaceous diving beetles and dragonfly nymphs (aquatic larvae) search for other insects and crustaceans to eat while ice covers the pond or stream. (Even salamanders, tadpoles and fish feed the diving beetle.) They are fine as long as the ice does not freeze to the bottom.

Parasitic insects - lice, for example - never experience cold weather, being protected form the elements by the warm climate provided by the fur, down, feathers, and hats of their hosts.

There are even a few hardy insects in the Maritimes that can be hound flying and crawling about during winter. Like skiers, they are most likely to be out on warmer, sunny days as spring approaches. Snow fleas are amongst the smallest lovers of winters. They are springtails, not fleas, but true to their namesake, they do jump. In and around wooded areas, they appear as black specks jumping on the surface of the snow as they forage for the spores of fungi and lichen. Snow scorpionflies look superficially like mosquitoes, but are not really closely related at all; instead of the familiar sucking proboscis, they have jaws for capturing small prey. Winter is the best time to observe these insects, as they reside deep within mosses at other times. Finally, the aptly named winter stoneflies are generally largest insects (about 1 - 2 cm) that can be found in good numbers crawling about on the snow. They mate at this time and their eggs are deposited in well-aerated stream and rivers.

The chief advantage to being out and about during winter is that there are fewer predators around. Most insectivorous birds are not yet back. The amphibians are still snoozing (see article by S. Friet). However, the insects are not totally safe. Shrews and moles are still foraging (see article by A. Hebda, K. Jensen). And if you come across a number of insects on the snow, you can be sure of encountering spiders, as well.

*Randy Lauff is President of the Eastern Mainland field Naturalists Society and a biologist at St. Frances Xavier University, Antgonish.

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