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Wendy Larsen, age 13, of Staten Island, N.Y., for her question:

How do mosquitoes live through the winter?

Sometimes Mother Nature seems to go out of her way to make our lives miserable. For example, summer is the season for picnics and outdoor fun. It also is the season for pesky mosquitoes. When winter is too cold for picnics and such, the mosquitoes have departed.

The teeming insects are cold blooded creatures that depend on their surroundings for warmth to keep going. As the weather cools, their body activities slow down and most of the adults perish before the first frosts. Through hundreds of millions of years, the vast insect world has developed methods to survive and start life anew in the spring.

Insects, of course, do not grow up in easy stages, as cats and dogs do. Instead, their life cycle is a series of different stages. Some survive through the winter as sturdy, weatherproof eggs. Others survive in the pupa stage. The mosquito is one of those that spends the winter in the egg stage.

Actually, the pesky critter is an amphibious insect. Only one quarter of its life is spent in the air as an adult. During this sunny phase of life, the winged female lays a tiny raft of mini eggs on the surface of some quiet pond or lazy stream. This floating raft is made of 50 to 200 white cone shaped eggs standing on end and packed shoulder to shoulder. The eggs may or may not spend the entire winter in this dormant stage. Even if you spotted the little raft, chances are you would never suspect that next summer it will become a squadron of flying mosquitoes.

After a few warm spring days, the eggs hatch and become wriggly larvae with hammer shaped heads. The mosquito larva is a fierce little tiger, famished for bits of plant and animal food. It is a good swimmer, always ready to attack other creatures that live in the pond. However, unlike most of the neighboring water dwellers, the mosquito grub is an air breather.

It must come to the surface to take in oxygen. In a week or so, the grub is ready to advance to its pupa stage. It rises to the surface and seals itself inside a leathery chrysalis. There it rests, hanging with head up and tail down.

During the next few warm days, the miracle of metamorphosis takes place inside the chrysalis. A few cells are retained to preserve the blueprint for the next body plan. The rest become a soupy mishmash. Gradually the old larva cells are reorganized to build a new adult mosquito. Then the chrysalis cracks open, the winged insect struggles free and takes to the air.

Through the summer months, the adult female lays brood after brood. The early broods have time to develop into adults and lay more eggs. Almost all the adults will perish before Christmas. But the last little rafts of floating eggs will stay dormant through the winter. Next summer's mosquitoes are in hiding, disguised as innocent looking eggs floating on our ponds and streams.

 

 

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