How Insects Survive Cold Winters
temperature is below freezing, insects and other cold-blooded animals
cannot be active. Some, like monarchs, migrate to escape the cold temperatures.
But even in the dead of winter in the far north, many insects are still
alive. Some are even very active! How can that be? In this
lesson we'll see how insects survive cold winters, depending on where
in their life cycle they are. Then we'll do some journaling, imagining
what it's like for insects to live through winter.
Are the Insects?
The easiest winters for insects are the ones when the temperature
gradually gets cold, stays cold, and then gradually gets warm as spring
arrives. But even in the worst winters, a LOT of insects survive. Where
are they? Many are hiding and even eating a little bit in micro-habitats
that aren’t as cold as the open air. They can be in such places
- the soil
logs, rocks, and fallen leaves
the wood of logs and trees
special bumps on plants called galls
windowsills, eaves, and attics of houses
do not hibernate. Hibernation is usually considered to be something
only warm-blooded animals do, when they allow their body temperature
to drop very close to freezing. Insects are cold-blooded, so it’s
not a change for their body temperature to be close to air temperature.
When insect eggs, larvae, pupae, or adults are inactive during the
winter months, with their growth, development, and activities suspended
temporarily, we call the dormant condition diapause.
Even though they stay alive, insects in diapause hardly move at all.
Insects that are somewhat active in winter are very, very sluggish.
Life Cycle Makes a Difference!
Different insects survive winter in all four stages of life.
Many insects, such as ladybugs, survive winter as adults, sometimes alone,
and sometimes in large groups. Ladybugs often gather in huge masses on
and near beaches for the winter. In fall and spring, before and after
they've survived the winter together, they're often seen in great numbers.
wasps and fly adults move into the eaves and attics of houses
or barns. Many other adult insect species hide in tree cavities,
under leaf litter, or under logs and rocks. The Mourning Cloak
Butterfly is usually the first butterfly we see in spring because
it spends the winter as an adult in tree holes or other shelters,
ready to emerge as soon as the temperature rises above freezing.
bees stay in their hives during the winter, and form clusters
when temperatures fall. They can raise the temperature by vibrating
wing muscles. A hive can use up 30 pounds of stored honey during
the winter. Just digesting and using the honey to stay alive
produces heat, and the action of vibrating the wing muscles both
produces heat and circulates it throughout the hive.
adult insects reduce the water in their bodies and produce glycerol,
a chemical that acts as an antifreeze.
Some insects overwinter as eggs. The mother insect usually lays these eggs
in protected areas. The praying mantis is one example. Eggs are fragile
and many freeze too easily to survive winter, so a great many kinds of
insects wait until spring or summer to lay eggs.
Some insects overwinter as larvae. Many of these are protected by leaf litter
or burrow deep into the ground. Some, like wood-boring beetles, chew their
way deep into tree wood. When insects lay their eggs in some kinds of plants,
the plants have an allergic reaction, and grow a large, thick bump around
the egg. This thick bump is called a gall, and it actually protects the larva
that hatches out. One kind of fly larvae that spends the winter in galls
is popular with fishermen who use it as bait in winter. Like adults, many
larvae produce glycerol to protect their tissues from freezing.
insects don’t spend any part of their lives as larvae.
Instead, when they hatch from eggs underwater they go through
the next life stage as nymphs. Nymphs can move
around more quickly and easily than most larvae and have more
complex bodies than most larvae. Some remain in this stage of
life for two or even three years. Dragonflies, mayflies, stoneflies,
mosquitoes, and some other flying insects spend the first part
of their lives in rivers, streams, lakes, and ponds. Ice may
cover the surface, but in the water beneath the ice, these insects
can actually be very active, feeding and growing.
Some insects, such as certain moths, overwinter as pupae, then emerge in
the spring as adults. Some of these pupae may produce glycerol, too,
to protect their tissues from freezing.
you’re in a big swimming pool filled with thick molasses
up to your neck. You have to work very hard to get anywhere,
movements are very slow. Do you think this is what it feels
like to be an insect or other cold-blooded animal in winter?
food be harder for an insect to eat in winter than summer?
How might breathing be more difficult in freezing weather?