Editor’s note: This letter is in response to an article republished from High Country News on July 5, 2023, titled “The Miller Moth is Hard to Love, But it Deserves Our Respect.”
A recent headline on your website declared that the army cutworm (miller) moth deserves our respect (Samuel Shaw, “The miller moth is hard to love, but it deserves our respect,” July 5, 2023). But the writer goes on to accuse army cutworms of acts they don’t commit and overlooks how helpful the larvae can be.
Native army cutworms can help us revegetate areas dominated by exotic invasive cheatgrass in the intermountain West. Cheatgrass blankets large swaths of the West in spring. The plants dry out to fuel summer wildfires that weaken native plants. During their periodic outbreaks, army cutworms can “clear cut” cheatgrass stands to create miles-wide bare areas ready for reseeding with native plants. Larval outbreaks typically follow a year of drought and a dry winter; wet winters kill larvae.
The moths Shaw mentioned, in Wyoming, Colorado, and New Mexico, probably emerged from pupae in the Great Plains. (Female moths laid eggs last fall, but didn’t build nests, as Shaw said.) After an extended drought, Kansas had an epic miller moth emergence early this spring. The wet winter Shaw credits for the moths was likely along their route to the northern Rockies. When rains produce abundant tempting flowers, the moths can linger on their journey longer than usual.
Although the larvae of many moth species eat corn, including the similarly-named armyworm, army cutworms rarely do, as Shaw claims. Army cutworms only exist as larvae from about December through May, so they primarily eat cool season plants (wheat, cheatgrass, canola, etc.). Corn is a warm season crop that rarely emerges early enough to encounter army cutworms.
Grizzly bears also outperform their cameo in Shaw’s piece. The bears have no trouble rolling over boulders in high elevation talus slopes to slurp up the fat-filled moths hiding underneath. The logs Shaw mentioned are rare where miller moths congregate.
Please, admire the gentle miller moth for its impressive migration and appreciate the army cutworm for its help revegetating cheatgrass-invaded areas.