As late summer nears, the days are getting a little shorter and mercifully a little cooler (is that wishful thinking?) Along with an abundance of mosquitos and tomatoes, it’s the time of year for caterpillars.
Some caterpillars are huge; sci-fi specters of horns, hair, and Day-Glo protrusions. These amazing creatures are rarely seen, in part because they tend to live in the tree canopy. But there are interesting caterpillars in our area that are easier to observe.
The most common cool-looking caterpillars to make frequent appearances in our gardens feed off herbaceous plants that grow low to the ground. There are three kinds that I observe more frequently than any others:
Black Swallowtail– these caterpillars are pale green banded with yellow-spotted black rings. They’re commonly found on garden plants like carrots, parsley, dill, and fennel, and also on ornamental plants like rue. The chrysalis is a papery dull grey that looks like a curled dead leaf.
Monarch– the caterpillar has distinctive white, yellow, and black bands, and delicate, crumpled black antennae. It feeds on members of the milkweed family, common field milkweed but preferably the more ornamental types in the Asclepias family, like tropical milkweed, butterfly weed, and swamp milkweed. Its chrysalis is a beautiful milky green with a magical stripe of gold leaf near the top.
Tomato Hornworm– This impressive caterpillar gets huge, almost four inches long, and it feeds mainly on tomato plants, but will eat leaves of pepper and eggplant as well. A type of braconid wasp often parasitizes the hornworm by laying a number of white eggs on its back. When the eggs hatch they burrow into the caterpillar to feed until they kill it. Hope you’re not eating as you read this.
We like to separate caterpillars into “good” and “bad” categories (except for those who assume all caterpillars go on the bad list.) This is somewhat arbitrary, since all caterpillars are leaf chewers, and will disfigure or destroy their host plants in the course of surviving. We seem to have decided that losing part of the parsley crop to swallowtails is acceptable, but that the hornworm on the tomato plant must be stopped! In reality, neither of these native insects will cause damage like the invasive tent caterpillar, especially in the home setting. And besides pollinating and decorating our gardens, butterflies and their larvae are a major source of nutrition for birds.
When a massive hatch of wormy looking dogwood sawflies defoliate my red-twig dogwood every year, I let them be. Most of the energy in the world is held in plant matter. Insects like caterpillars are tiny transformers, converting that plant energy into a form that is usable by higher life orders.
And besides, once the caterpillars get picked off the dogwood pushes out new leaves. It doesn’t seem to mind going partially nude for a few weeks every summer.