Where do bugs like flies go when the weather gets cold, so they can appear like magic when it gets warm again? asks Jonathan Conway, of Syosset, NY.

Unfortunately, many insects don't survive the freezing cold of winter. Others, however, have come up with clever schemes to hang on until spring.

For example, cluster flies sometimes hide out in the nooks and crannies of a warm house or barn over the winter, venturing out to fly around only on milder winter afternoons.

Mosquitoes, like bears, hibernate through the winter cold. Adult mosquitoes look for dark, damp, hiding places--like your basement--to spend their winter vacation. In spring, the females slowly become active, flying around looking for food (fresh blood). Once they've had their blood meal, they're ready to lay eggs, and hatch a new crop to plague us during the summer.

Some mosquito species do things differently. In summer they lay their eggs. The adults die off. But all through fall and winter the eggs lie still, actually freezing when the weather turns nasty. When the warm rains of spring finally come pelting down, the eggs thaw and hatch.

Some water-dwelling insects burrow into lake and river bottoms for the winter, and some beetles hibernate in tree bark. Certain honeybees cram together into a ball, using their wing muscles to generate heat and keep the temperature above freezing in their hive.

Other insects harden themselves to the cold by changing their body chemistry. For example, certain caterpillars in the far north produce a substance similar to car antifreeze, and can survive even when the temperature drops below -100 F. Like birds, some insects migrate in the fall, escaping the cold for warmer places. Locusts are migrators. So are some species of butterflies, moths, dragonflies, ants, termites, bees, wasps, and ladybugs.

The monarch butterfly, the beautiful orange-and-black insect seen in North America in the summer, is one of the most famous migrators. For many years scientists knew that the butterflies took off for the south in cool weather, but no one knew where they spent the winter.

An entomologist named Fred Urquhart spent more than 40 years trying to solve the mystery of migrating monarchs. Urquhart devised a way to tag individual butterflies by attaching lightweight adhesive strips to their wings. He convinced hundreds of people to help him look for the butterflies on their flights. Finally, he was able to narrow the search for their winter resort to the Sierra Madre Mountains in central Mexico.

In January of 1975, when snow covered the summer homes of the monarchs, one of Urquhart's friends hiked into a 20-acre area of the mountains, and was flabbergasted by what he saw. More than 1,000 trees were covered from top to bottom with a living carpet of monarch butterflies, half-asleep. There were so many butterflies piled onto the trees that limbs sometimes broke under their weight. The mystery of the missing monarchs was solved.