HOW COME?: Winter bugs insects in lots of ways

Where do insects like flies and mosquitoes go in winter? asks a reader.

Recipe for a snowman (besides the snow): Hat, carrot, charcoal, corncob pipe, scarf, flea collar . . . Wait, what? You say your snowman doesn't have fleas? Look closer, and you may see a few tiny, jumping specks: snow fleas, one of the few "insects" active in winter. But here's the rub - snow fleas aren't really fleas. And they're not full-fledged insects, either.

The true insects - the flies, mosquitoes, ants, bees, butterflies - are either long gone or lying low. Many adult insects don't survive the freezing cold of winter. But many migrate; others hide and hibernate.

Flies often hide in the nooks and crannies of a warm house or barn over the winter, venturing out to flit around only on milder winter afternoons. Some adult mosquitoes look for dark, damp, hiding places - like your basement - to spend the winter. Other mosquito species do things differently. In summer they lay their eggs, and the adults die off. Through fall and winter the eggs lie dormant, actually freezing when the weather turns cold. In the spring, the eggs thaw and hatch.

Besides surviving as eggs, some insects make it through the winter in their immature forms, as larvae, nymphs or pupae. Caterpillar larvae may wait, buried under leaves; the larvae of cicadas and June bugs and fireflies burrow into the soil. Dragonfly and mayfly nymphs live in streams and ponds, even when the water is topped by ice. And the pupae of certain moths stay attached to branches, waiting for spring. Meanwhile, tomato hornworm pupae rest several inches underground.

Adult insects look for warmish spots to hibernate, like holes in tree bark; under rocks, leaves, and fallen trees; and in barns, attics, basements and the walls of houses. (Think ladybugs and wasps.) Honeybees stay warm in their hive homes, snuggling up in a tight ball, using their wing muscles to generate heat.

Like many birds, some insects migrate in the fall, escaping the cold for warmer places. Locusts are migrators. So are some species of butterflies, moths, wasps and other insects. The orange-and-black monarch butterfly, found across the United States and Canada in summer, is a famous migrator. Hundreds of millions of monarchs leave in the fall, flying up to 3,000 miles to their winter home in Mexico's Sierra Madre Mountains.

Many insect species that stay put, from beetles to bees to butterflies, harden themselves to the cold by changing their body chemistry, allowing a kind of natural antifreeze to build up in their tissues. But these insects also remain mostly dormant, to conserve energy and stay warm. Snow fleas, on the other hand, stay active throughout the winter.

Snow fleas are actually springtails, tiny bouncing bundles that resemble dark specks on the snow. While springtails look and act like tiny bugs, they are considered only "insectlike," since their eyes and abdomens don't match those of true insects. Snow fleas range into the Arctic and Antarctic, their potent antifreeze allowing them to thrive in the cold. By studying the antifreeze protein, scientists have developed a synthetic version, which might help extend the life of human donor organs for later transplant.