FAIRFIELD COUNTY, Conn. -- In cold climates, insects seem to disappear when temperatures plummet. So where do they go? Depending on the type of insect, there are different strategies for surviving the cold.
While some insects migrate to a warmer climate, like Monarch Butterflies and a small percentage of dragonfly species, most of the insects in our landscapes stay put in the winter. Here’s how they do it.
In general, insects either have a strategy to avoid freezing or have a tolerance for freezing. Many insects produce an antifreeze-like substance in their bodies called glycerol. Glycerol prevents the water in the insect’s tissue cells from freezing and expanding, preventing tears in the cell walls.
Hibernation as Adults
Quite a few insects hibernate in our yards as adults. The Mourning Cloak Butterfly seeks out a protected space for winter - under the loose bark of a tree, in holes in tree trunks, or under leaf litter. Keep that in mind before you decide to “clean up” your leaves.
Lady bugs also overwinter as adults, often in sizeable groups. They can be found huddled under rocks or tree bark, in leaf litter, or in the pithy stems of plants. Keep your perennials and grasses standing through winter, and cut them back in spring. You never know what valuable insects will benefit.
Most native bees die by late fall, but healthy, mated queen bees overwinter. A mated queen bumble bee will seek winter shelter in a variety of safe places. She may find a small cavity just under the ground, using loose soil and leaf litter. Or, she might find an opening in a stone wall, cover in a brush pile or wood pile to spend the winter. What overwintering sites can you offer her? Skip the “fall cleanup” which may prevent her survival.
Overwintering as Larvae
Some caterpillars, like wooly bears, overwinter in their larval stage. They are actually capable of freezing in cold weather, thawing out when the weather warms, with no harm done to their bodies. Once again, leaf litter will give wooly bears a safe place to overwinter.
Overwintering as Pupae
Most butterfly species overwinter as pupae, suspended from plant stems, small branches or dead sticks in your yard. Butterflies like Swallowtails, Question Marks and American Painted Ladies use this strategy. Most moths overwinter in spaces underground as pupae. Moths in the Silkworm family, like the Cecropia Moth, have strategies to overwinter in cocoons often attached to the trunk of a host tree.
Overwintering as Eggs
Some insects lay eggs that can survive winter. Those that do, often envelope the eggs in a protective coating.
Overwintering as Nymphs
The nymphs of many dragonfly species are actually active in the winter, living in ponds and streams under the ice. They feed and grow throughout the winter.
Why Help Insects Overwinter?
It is estimated that at least 90 percent of the insects in an average home landscape are either beneficial or benign. Yes, there are insect pests, but in most situations they can be kept in check with “nature’s pest control” - natural enemies, like lady beetles, wheelbugs, predatory wasps, etc.
And, if you love birds, consider this fact from entomologist, Dr. Doug Tallamy: 96% of all land birds in the U.S. feed insects to their young. Want more songbirds? Make sure to support the insects that they need.
Kim Eierman, a resident of Bronxville, is an environmental horticulturist and Founder of EcoBeneficial. She teaches at the New York Botanical Garden, Brooklyn Botanic Garden, The Native Plant Center and Rutgers Home Gardeners School.
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