Winter World_ The Ingenuity of Animal Survival - Bernd Heinrich [86]
The carpenter ants are able to use the dry wood, because unlike the stationary beetle larvae, they are highly mobile and bring water into their nests to moisten the wood, if need be. I’ve found them living in still-upright balsam fir trees in winter and, since ice crystals are mixed in with the masses of comatose ants, they need some other strategy besides supercooling to survive winter.
Both the ants and the beetle larvae spending the winter inside tree trunks endure temperatures close to those of the ambient air. I’ve brought both into the house and warmed them up, but unlike flies, which spring to life almost immediately when warmed, the ants and beetle larvae seem stone dead, even after being warmed. Only after a few days at room temperature do they gradually show movement, eventually resuming full activity. But when I have taken these revived ants and beetle larvae and stuck them out in the cold from whence they came, they died quickly. Clearly their survival is dependent on their antifreeze-induced torpor. The ants and beetle grubs, when cold-adapted, contain large amounts of glycerol or other sweet-tasting antifreeze (I have not tasted the flies), which prevents ice crystals from forming in their bodies and probably pickles them into inactivity. It takes a long time at elevated temperatures to get that antifreeze out of the blood.
The other winter cabin guests—I’m thinking of three species in particular—are beautiful and more benign in habit. When the cabin is heated, for example, they don’t have the annoying Pollenia’s tendency to hover around the bed light and then, when it’s turned off, to dash under the covers and buzz there rudely.
The first of these three species, the mourning cloak butterflies (Nymphalis antiopa), usually remain in crevices outside and only rarely make it into the cabin. In the fall I commonly see one or two fluttering under the cabin roof. The second species, the multicolored Asian ladybugs (or ladybird beetles), has arrived here in numbers only in the past few years. These occupy the cabin by the thousands in some years, and by only dozens in others. First imported from eastern Asia by the U.S. Department of Agriculture in the late 1980s as a biological control on pecan aphids, this species (Harmonia axyridis) was later introduced to other areas, including the Northeast, to control similar pests. It has since spread far and wide on its own, to most areas of the United States and to parts of Canada. Like many species of ladybirds (there may be some four hundred ladybug species in North America and three thousand or so worldwide), these beetles all have handsome black coloration. Those ladybugs endemic to North America species have specific color patterns, but in the Asian species, virtually every individual is uniquely colored. Each bug’s background hue can be deep red, or orange, or yellow, and it may have no spots, tiny black dots, or spots that coalesce into black bands. (Another species that very rarely overwinter in the cabin is uniformly coal black with one red spot on each wing cover.) The colors serve as warning to stay clear; multicolored Asian ladybugs secrete a foul-smelling fluid when crushed. But even certified bug-haters find it hard to want to kill ladybird beetles. Besides being prettified in handsome colors, they have soft rounded curves, little legs, and petite feet. They are about as cute as any bug on the planet. Adorable, even. But cuddly, they are not. We found that out after they moved into our Vermont home in the fall by the tens of thousands (literally), and then stayed for over six months—despite all our best efforts to try to evict them.
A sample of multicolored Asian ladybird beetles from my window.
Our family made a most intimate acquaintance with these beasts during the winter of 2001–2002. A few pesky forerunners had appeared in our Vermont home in previous years, when they were an almost