One of the best things about winter, for many people, is the lack of bugs. It's grown too cold for the mosquitoes, the ladybugs have finally stopped swarming around windows and the clouds of gnats that characterize summer in the Midwest have disippated. The question hardly anyone thinks about, however, is the following: where do all the insects go? There are many tactics insects use to escape the cold, and when the insects use these tactics, they are pretty much invisible to human notice.
Many insects hibernate as adults, such as wasps and ladybugs. They usually hibernate in large groups, and they seek out sheltered hiding places, such as in attics or under eaves. Hiding in decomposing leaves on the ground is also a common habit, as well as hibernating in holes in trees. According to the Smithsonian Institute Encyclopedia
, some butterflies like the Mourning Cloak butterfly are able to resist the cold by reducing water in their body, and then making glycerol to use as antifreeze. Bees tend to stay in groups inside their hives, and they can vibrate their wing muscles to keep warm. They also eat the honey they have stored, giving them energy to keep themselves from getting too cold. Ants and termites huddle together in colonies as well, similar to bees.
Other insect species spend the winter as larvae or pupae, emerging as adults in the spring. This allows them to get most of their growth out of the way while they are hibernating, and they can flourish as adults when it's warmer and there is more food. Mosquitoes, for instance, hibernate as eggs, and once the cold of winter starts to thaw, the eggs begin to grow. This is why, when heat and humidity rise, the mosquito population multiplies. They are all hatching out of their eggs and reproducing even more.
Pro tip: If you have a pond in your back yard, a good way to keep the mosquito population down is to introduce goldfish into the pond in early spring, when the water is defrosted all the way, and they will eat the mosquito eggs and larvae.
Insects can also create galls, which are orb-like formations on the side of trees. They burrow into the tree and suck the inner plant tissue, causing the tissue to swell and form a sort of bubble. They sequester themselves inside the bubble, and the bubble of plant tissue protects them from the elements during the winter. Sometimes insects do come out in winter when the temperature rises above 45 degrees Fahrenheit, but this is rare. They come out for the warmth of the sun, but once the weather goes back to a colder temperature, they go right back inside their hiding place. These insects can often be found coming out of dead or dying trees, since a lot of insects burrow into holes inside the bark to shield themselves.
So, insects may appear hidden during the winter, and that definitely has an advantage for humans, but they are still there. They just have very clever ways of hiding themselves.