Critter Close Up: The Miller Moth

July 23, 2013 at 9:17 pm Leave a comment

Author: Teisha Rowland

You may have seen them flying around your home on some warm summer nights. Or perhaps some even snuck inside of your home, being attracted to the lights! Either way, you’ve already encountered Colorado’s Miller Moth, but what do you know about these commonplace critters?

  • Have I seen one? On summer nights you’ve probably seen these little moths hovering around lights, which they’re attracted to. You may also have seen groups of swallows at intersections that are feeding on these moths, which likely hid on the cars and emerged when they stopped. With a wingspan of 1.5 to 2 inches, these gray to light-brown moths have variable, nondescript markings on their wings, except for a few tiny, kidney-shaped spots, as seen in the picture shown here.
  • Who’s their family? The Colorado Miller Moth (Euxoa auxiliaris) is the adult form of the army cutworm. The army cutworm belongs to a large family of moths, the Noctuidae, or owlet moths. Over 1,100 species of moth from this family call Colorado home.   
  • Where’s their home? Miller Moths live in Colorado and some nearby states. They’re natives to this region. In Colorado, the caterpillars grow up on the plains during the winter and spring. The adult moths will often fly west hundreds of miles to the Rocky Mountains to follow blooming flowers and avoid the scorching summer heat. It’s during this migration process that people who live along the Rocky Mountains notice the moth “invasion.” This mass migration typically lasts for a few weeks sometime between April and July, varying from year to year. The moths will seek a dark shelter during the day, are attracted to lights at night, and are frequently seen as a nuisance around homes. The surviving moths fly back to the plains during the early fall to lay their eggs and repeat the cycle.
  • What’s for dinner? The caterpillars grow up on a diet of wheat, alfalfa, and other plants. Consequently, they can be a serious crop pest, but there’s no need to worry that the moths will reproduce in a home and damage furniture.  The adult moth spends the entire summer eating nectar from flowers.
  • Whose dinner are they? The caterpillars are eaten by beetles, wasps, and birds. The moths are a food source for bats, birds, and bears. In fact, their fat-rich bodies can be an important part of grizzly bears’ diets.
  • Other fun facts: The army cutworm is aptly named. “Army” refers to the fact that these caterpillars may be found in large groups, like an army, and impressively cross fields or highways together. “Cutworms” are a type of caterpillar that typically cuts plants down near the base of their stems.
  • At Butterfly Pavilion: At Butterfly Pavilion you can see several moths, including the Luna Moth (Actias luna) and the African Moon Moth (Argema mimosae). These belong to the Saturniidae family, a group that contains some of the largest moths in the world.
  • Find out more: Check out the following resources to learn more about Colorado’s Miller Moth:


Is there a critter you’ve seen around your home or backyard that you’d like to see in a Critter Close-Up? If so, please contact us! If you aren’t sure what kind of critter it is, you can include a photograph and we’ll pass it on to our experts to identify.


[Image from: We’ll want to attribute the image to Whitney Cranshaw, Colorado State University, It’d be best to crop the image and enlarge it so that the kidney-shaped spots are more visible.]Image


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