The miller moth, which is a mature army cutworm, is a common pest in Colorado.
These moths are usually gray or brown with two characteristic light spots on each wing. They can be extremely annoying when they get into homes and cars, but they do not breed indoors or eat clothing, and generally die within a few days.
These pests overwinter as larvae in the soil, primarily in alfalfa and wheat fields in eastern Colorado. In the spring, caterpillars emerge to feed and complete their life cycle. Moths emerge in May or June, with the majority emerging during a very short period.
They migrate to higher elevations in the mountains to find food, crossing heavily populated areas of the state. If moths get to the mountains, they usually stay there until late summer or early fall when they return to the eastern portion of the state. Fall migrations are smaller and less frequently observed than the spring migration.
Experts believe that miller moths get distracted from their normal flight pattern by light at night in urban areas -- porch lights, security flood lights and street lamps.
insecticides are not effective at controlling these pests. The best controls are to seal any openings in the home, reduce the amount of lights at night and guard doors as people come and go to prevent moth entrance.
Once inside a home, moths can be controlled with a fly swatter or vacuum cleaner. Keeping a light suspended over a bucket of water during the night also can trap moths. You may also wait for the insects to die on their own in a few days.
Remember that these insects are a nuisance, but pose no danger to humans, plants, clothing and fabric.
For more information, see the following Colorado State Extension fact sheet(s).
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Updated Friday, April 19, 2013