cutworm
A soil-dwelling caterpillar that cuts and kills young plants.
A cutworm is a type of caterpillar that lives in soil and comes out at night to feed on young plants, often cutting through their stems right at ground level. The name makes perfect sense once you see what they do: a gardener might come out in the morning to find healthy seedlings toppled over, their stems cut as if with scissors, with the cutworm hiding in the soil nearby.
These plump, gray or brown caterpillars curl into a C-shape when disturbed. They're the larval stage of several species of moths, and they cause problems for farmers and gardeners by destroying crops like tomatoes, corn, and beans. A single cutworm can destroy multiple seedlings in one night, which makes them particularly frustrating pests.
Gardeners fight cutworms by placing protective collars around young plants or by going out with flashlights after dark to catch the culprits in action. The word cutworm works as both singular and plural: you might find one cutworm in your garden, or discover that cutworm have damaged an entire row of plants.