By Allison Holzer, Interpretive Naturalist at North Mississippi Regional Park
Few people worry about what insects do in the winter time. And unless you have an invasion of ladybugs or the like, you are probably just as happy to forget the mosquito-laden evenings of summer. We tend to think of winter as the time when insects die and we are free to venture outside without bug spray, but our six-legged friends don’t simply kick the bucket when the temperatures drop. After all, they must find a way to somehow survive until the following summer, and it turns out that insects are quite varied in how they deal with the cold. If you were a Minnesota insect, here would be your options for survival:
Migration. Yes, it’s true—some insects, like monarch butterflies, green darner dragonflies and others are strong enough to fly south for the winter just like the birds. This might seem like an appealing option–after all, who wouldn’t want to spend the colder months in Mexico or Florida? It is, however, a big deal to fly 1500 miles south; the journey is long and dangerous, with hungry birds, cars and lack of food to deal with. As many as 50 percent might die during migration. This leads us to our second option…..
Go ahead and freeze. Usually we think of freezing an insect as a really good way to kill it, but some insects’ bodies are designed to freeze and still survive. Wooly bears, those fuzzy brown and black striped caterpillars, are an example; they spend the winter at the soil surface, under leaves or bark. Their bodies allow ice to form in-between their cells, but not inside their cells, and their long hairs help ice form on the outside of their bodies to keep them at a relatively stable temperature. As long as they don’t go through too many winter thaws, ice crystals will not puncture their cells and they will survive.
Freezing is also risky business. Ice draws water out of an insect’s body, and if they become too dehydrated they will die. In addition, if we have too many freeze/thaw cycles over the winter, they do not survive as well. There are very few insects in Minnesota that use this strategy.
Avoid freezing. This is the most popular option among Minnesota’s insects, and there are many ways that they are able to avoid the cold. The most obvious is to go deep enough in the soil that they are below the frost line. Some grasshoppers tunnel deep into the ground to lay their eggs before they die in the fall, and some beetle larvae overwinter in soil chambers as well.
If an insect’s life cycle includes water, this provides an easy out–creatures such as mayflies and dragonflies can simply be sure that they have some eggs or larvae in a body of water that doesn’t freeze. Here by the Mississippi, the winter riverbed is occupied by dozens of species that we will see flying through the air come summer.
A fancier but very effective strategy is for an insect to produce antifreeze in its body. Queen bumblebees, butterflies in their chrysalises, fly larvae, mosquitoes, ladybugs and many more use the cooling autumn months to gradually change their body chemistry. By the time temperatures drop, they have enough antifreeze circulating through their cells to prevent them from freezing. The only downside is that it takes many weeks to reach this point, so a sudden cold snap can leave insects out in the cold.
So, those are the choices. While a few species of insects do leave us, most are there out in the cold, marking time until warmth returns.
Join us at Kroening Interpretive Center in North Mississippi Regional Park for the following nature programs. Reservations required, call 763-559-6700. New Year’s Day Snowshoe Hike, Friday, January 1, 1-3 p.m., ages 8+, $5. Basic Winter Survival, Saturday, January 9, 10 a.m.-noon, ages 8+, $8/set of snowshoes. Dream Catchers, Saturday, January 16, 1-3 p.m., all ages, $5. Snowshoe along the River, Saturday, January 23, 10 a.m.-noon, ages 8+, $5.
For young children and their adults: Snow and Ice, Thursday, January 14, 9 a.m.-noon, ages birth-6, $5 per person. Mystery Track Puppet Show, Wednesday, January 20, 10-11 a.m., ages 2-6, $4 per person.
Free Family Fundays: Come by on Sunday afternoons anytime between 1-3 p.m. for a free family program, all ages welcome: Tales of Scales on January 3, Winter Campfire on January 10, Snow and Ice Art on January 17, Static Electricity and Magnetism on January 24, and Lunch with the Animals on January 31. In addition, there will be a free River Walk on Saturday, January 2 from 9-10 a.m. Reservations are not required for the above free programs. Call 763-694-7693 for info or visit Threeriversparks.org.