Moth of the Week: Army Cutworm Moth

Meet the Army Cutworm, Euxoa auxiliaris. However, if you live in Colorado or surrounding areas, the chances you’ve seen one is 100%. Coming from the family Noctuidae, yes, in fact, these are the Miller Moths that somehow make it into homes every summer. Despite how much they’re seen, though, there is surprisingly little common knowledge about them. While drab in appearance, they’re fascinating and often misunderstood creatures.

Miller Moths have a particularly fascinating lifestyle. They are migratory, but can also live in harsh winter temperatures. Eggs are laid in the late summer and early fall, where the new caterpillars soon emerge. They feed on a variety of crops including winter wheat and can sometimes become pests, but they are easily controlled. They do not actually overwinter, which means that they pupate over the cold season. Instead, they remain as caterpillars, sleeping and emerging to feed when temperatures are warm enough. Caterpillars are social, and they can often be seen crawling together in large bands, hence their “army” moniker. Cutworms are full-grown by mid-spring, where they will then burrow into the soil and pupate, safe from most predators. Around five weeks later, the adult moth will emerge, and large populations will migrate to high altitudes, where they do not mate but instead feed on nectar in a period called diapause. The reason for this migration throughout several states is so they will have plenty of fresh flowers for feeding. The moths finally move to lower elevations and mate, laying their eggs on host plants.

There are many unfavorable myths about these moths. One is that they eat clothing. No, they do not. That is an entirely different family. While the caterpillar can be a garden pest, they are pollinators. Also, they will not lay eggs in your home—they’ll either find their way out or die of starvation. Adult moths literally do nothing harmful. They are NOT trying to attack you; they are simply disoriented from lights, and they carry no disease. They are also sensitive and frightened by noises such as keys rattling, as they interpret those sounds to be bat sonar. Miller Moths are vital to the ecosystem, providing food for all predators from birds to even grizzly bears as their bodies are high in healthy fats.

Do NOT use pesticides on these moths. They are ineffective. Instead, catch them in a cup and let them outside. The moths—and many other animals—will thank you! Now, if you excuse me, I have some Millers to catch and let outside.