In an early spring e-blast, we posted a picture of this large, somewhat innocuous looking caterpillar that showed up on top of six inches of snow in my back field.
The phone app iNaturalist, a handy app for identifying many things in nature, identified this generally as something in the Cutworms and Dart Moths family. It noted that some in this family are generalist feeders, meaning they feed on anything, which can make them something of a pest.
I soon received an email from CREA’s good friend, David Reed, our local invertebrates experts. The following information on our friend the cutworm is all thanks to David.
The so-called ‘winter cutworm’ is a common but minor pest in Europe. It is not native to North America, first arriving in Nova Scotia in 1979. It was found in Michigan in 1998 and first seen in Oregon in 2001. Apparently the moths cover some ground, since we can assume the caterpillar is neither sprinter nor distance runner.
Since then it has spread in the US as far as Texas and California. Only rarely is it reported to cause significant crop damage. They cutworms overwinter as last-instar caterpillars and pupate in the spring. (‘Instars’ are developmental stages of insects, in between molts, that enable them to grow or change form until they reach maturity.) They live primarily on grasses but will eat almost anything in your garden including the weeds.
Most interestingly, the caterpillars generate their own glycol antifreeze to prevent freezing in the winter. As they move about in late-winter or spring, they metabolize that sugary glycol at which point they are no longer protected from freezing.
As David noted, “Isn’t nature marvelous?”