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Question: Where do bugs go in the winter when they all die? And how do they come back in the summer?
A good question, Peter, with a number of answers! In fact, they don't all die of course – the bugs are here, we just don't see them. Each insect species living locally has developed a strategy to survive the winter.
In most cases, some stage of the insect's life cycle overwinters here, depending upon the species of insect. Many overwinter as adults in sheltered spots (under leaf litter, in the soil, under bark, etc.). These include the lady beetles, (which may form large aggregations), and bark beetles (wintering in chambers under tree bark). The mourning cloak butterfly, a common butterfly in our region, hibernates as an adult in tree cavities or under loose bark and other sheltered spaces, and may emerge on warm early spring days while snow is still on the ground. Honeybees spend the winter clustered in their hive, eating honey and generating heat by vibrating their wings. Other insects such as butterflies, moths, flies and beetles overwinter as papae or larvae. Other insects overwinter as eggs, such as the foamy tan egg masses of the praying mantis found on weed stems in the field, or the dark gray clusters of tent caterpillar eggs on the twigs of apple and cherry trees. While finding suitably sheltered spots to spend the winter contributes greatly to survival, many insects also synthesize "antifreezes" such as glycerol to help protect themselves from fatal freezing. Other insects synthesize antifreeze proteins, which bind to ice crystals that do form, inhibiting their further growth.
Finally, like birds, some insects escape winter by migrating to warmer climates. In our area, the most prominent insect of this type is the monarch butterfly. These migrate south in the fall to a small mountain region in Central Mexico. Come spring, these butterflies fly north, laying eggs on milkweeds along the way, to start the new generations for the year.
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