The Friends of the Wild Flower Garden

P. O. Box 3793
Minneapolis MN 55403

Baby it's Cold Outside

by Diana Thottungal

EVER wonder what happens to the mosquitoes? Not that you miss them, but where are they all winter? And the frogs? Fact is, some winter adaptations are quite familiar, like heading south, heated homes and warm coats. But some others are just plain peculiar.

Chorus Frog
The Western Chorus Frog can survive freezing in winter.
Frogsicles and Bugsicles

One of the strangest is allowing one’s self to freeze solid. Comes winter and some of our famous Spring Peepers, Wood Frogs and the Western Chorus frog do precisely that. Drop them and they break. Let them thaw slowly, and they hop merrily away. How do they pull this off? Most of us don’t freeze live critters, but we do sometimes see the effect of freezing a veggie.

The thawed result is a limp collection of what the microscope would reveal to be split open cells that broke as the water expanded when freezing. To see a demonstration, put some water in a small container and note the level. Check back after it freezes and you’ll see that the ice level is higher than the water level had been. That expansion is what splits the cells. So the frogs first bury themselves to get some insulation, suck enough water out of their cells so that they can freeze without splitting and then send glucose or glycerol into the cells to help protect them. And, should one be so unkind as to dissect a frozen frog, that water, sucked out of the cells, shows up as flat plates of ice located outside the cells in the body of the frog. Only cold-blooded creatures that have no way of keeping their insides warmer than the outside need this adaptation.

Speaking of Anti-Freeze
The Western Chorus Frog can survive freezing in winter.

The other kind of anti-freeze is, of course, the stuff you buy in bottles for your car. It’s a chemical called ethylene glycol, and some insects make their own. Other insects make glycerol or sorbitol, which act pretty much the same way. Thus the Mourning Cloak butterfly, hiding under bark during much of the winter, uses sorbitol to prevent freezing on super cold days. But it also uses those superb dark wings as solar collectors, basking on warmer days and even flying. But wait, it takes energy to fly, and there are no flowers blooming to provide nectar. Do you really want to know what this lovely, delicate butterfly feeds on in the winter? OK ... dung. But, also, in the early spring, it feeds on tree sap, as shown in the photo taken April 30, 2008. The other butterfly in the picture is a Hackberry Butterfly, which has its own story to tell.

When the Buzzing of the Bees is a Kind of Anti-Freeze

Bees live outside in the cold and can survive the winter. They combine several tricks to make it work. First of all, they huddle and cuddle so a minimum of heat wanders out of the hive. Then, being cooperative, the cold bees on the outside of the huddle get to move to the inside. But there’s more. They buzz (more scientifically, they vibrate).

That buzz generates so much heat that the inside of the huddle can be as much as 80˚F. As a matter of fact, two stories. The caterpillars of this butterfly huddle together on a cluster of Hackberry tree leaves. The leaves have been bound to the twig and each other with silk webbing. So, if in the winter you look up at a Hackberry and see a brown cluster of leaves hanging on, odds are that you are seeing the winter home of the caterpillars who have further protected themselves with their anti-freeze.

In addition, at least some adults hibernate. That’s who you see on the tree. Those that make it through the winter are hungry when it warms up enough to fly.

Why do mosses stay green all winter? Because they can!

Guess what else produces anti-freeze. Yep, those little inconspicuous mosses. Which would be just a bit of trivia, unless you consider that reindeer eat their anti-freeze in the form of those not otherwise very nutritious mosses, which most critters find indigestible.


The tiny Duckweed plants that cover lakes and ponds all summer disappear in the fall and reappear in the spring. Their secret? With the onset of fall the leaves produce tiny mini-leaves that sink down to the bottom of the water and live there until spring, when they rise.

In other words they migrate up and down with the seasons. Coontail, the water plant living in Wirth Lake, also sends winter buds down to the bottom of the lake.

Oh, about those mosquitoes: They overwinter either as underwater eggs or adults hidden in the leaf litter and protected with glycerol anti-freeze.

Duckweed decorating a slider turtle. Duckweed hides at the bottom of the lake to escape freezing. Joe Yatsy 2008


Diana Thottungal

Diana Thottungal is a naturalist at the Eloise Butler Wildflower Garden. Photos by Diana Thottungal unless otherwise credited.

Note: This article was published in the Fringed Gentian™, Winter, 2009, Vol. 57 #1. Vol. 57, #1.