The Backyard Naturalist – Signs of Life in Winter
Descending from fall into winter, losses seem to accumulate. You catch sight of what you think is a phoebe, tail bobbing on a fence post, and then you realize it’s just rain sluicing off the roof and repeatedly hitting a leaf, bouncing it up and down. Then you think how you can’t remember the last time you saw a phoebe, and that’s fall. Someone’s cellphone rings at work and it’s a cricket-chirping noise, and you realize you can’t remember the last time you heard a real cricket, and it’s been weeks since the one in the cellar somewhere by the woodstove went quiet, and that’s winter.
The cold months mete out a sensory deprivation. Dark, snow-muffled. Animals, especially the insects, are notable mainly for their absence. But the laws of conservation of matter cannot be disobeyed, and all those throngs and hordes of insects have to have gone somewhere. Many died, it’s true, some ending up in the bellies of those departed phoebes and warblers bound for Florida or South America. Some fell to the earth and will overwinter in the soil. Some, like the Collembola springtails, forge right through the winter, looking like an animate sprinkling of pepper on the snow, flinging themselves around at the bases of trees, even in the depths of February.
The most conspicuous evidence in winter that insects were ever on the landscape may be galls. Galls are deformations in stems and leaves that plants build around invading insects burrowing into their tissues. Galls are tumorlike, both in appearance and in physiology, with the plant tissue growing rapidly and seemingly unchecked as if it were a cancer. The insect gains protection from the thickening wall of plant matter forming around it, and can shelter within it for the duration of winter. Among the most common in my garden are the elliptical goldenrod stem galls. Each type of gall harbors its own sort of insect; for this goldenrod gall, it’s a moth. The gall begins to form when a caterpillar burrows deep inside the plant stem and takes up residence. The goldenrod responds, building around the larva layer by layer, wider at the center and tapering to the stem at both ends. Inside, the larva continues to feed until July, when, out of instinct that looks like foresight, it digs an escape hatch in the wall of the gall and then plasters it over with silk and plant matter, leaving a door for its future form to leave by. Caterpillars are eating machines, but as moths they lack the jaws for the work, and without a weakness built into the gall, they would be entombed inside.
If you read about the life history of this insect, you will encounter a curious lack of clarity over whether the larva stays inside the gall all winter and emerges as an adult in spring, or if it completes the entire process and has vacated the gall by August or September at the latest. The gall itself, if found in the winter garden, is, then, something of a Schrodinger’s box. If you slice the gall open lengthwise, you may find it empty, a silk-lined chamber abandoned by its one-time tenant. But if the larva did not manage to become a moth before winter came, it may be there still, tucked into one end of the double-pointed gall as if into the stern of a boat. You will have doomed it to death by bisecting its chamber into two neat, tiny kayaks of woody stem, but sometimes, in your craving for signs of life in the winter landscape, it will be an urge you cannot resist.