Miller Moth Migration

What’s the deal with Miller moths this time of year?

As the weather warms and spring descends on Colorado, Front Range cities and towns are beginning to witness the migration of Miller moths. These winged creatures are embarking on a journey from now through early June, flying from the plains to the mountains, and often catching the attention of Coloradans in the process.   The migration of Miller moths begins on Colorado’s high plains, where adult moths lay their eggs underground. These eggs hatch in early spring, giving rise to army cutworm caterpillars (Euxoa auxiliaris) about the size of a grain of sand. These tiny creatures feed on vegetation, cutting through stalks of wheat and corn, and rapidly growing to about the size of a child’s forefinger. Then they turn into moths with wings, commonly called “Miller moths” due to their fine scales that rub off, resembling the dusty flour on millers’ clothing. During their migration, these resilient insects are capable of flying over 100 miles from the plains to the mountain ranges. Despite their large numbers and occasional presence in our homes, Miller moths pose no threat to humans or to our pets. They do not carry diseases, sting, or bite. In fact, their presence attracts animals that rely on them for food, like birds, who we often like to see in our backyards.  Colorado is home to about 1000 known species of moths. However, compared to their more charismatic butterfly cousins, moths remain heavily understudied. Moths are not pests, but fill a vital role in our ecosystem, serving as a food source for birds, bats, spiders, and even bears. Additionally, moths function as pollinators, facilitating the reproduction of plants, which we require to sustain our economy, environment, and food systems. 

As moths are nocturnal, they pollinate plants that daytime pollinators, such as bees, cannot, or cannot do nearly as efficiently. Moths are responsible for propagating crops worldwide, worth billions of dollars.

We can help these important animals and keep them away from our spaces by being mindful of our use of artificial light. Moths are nocturnal creatures; they rely on light from the moon and stars for navigation. When they see artificial lights such as a porch lamp, they become lost and confused and attempt to use it as a navigational source, thinking it is the moon or another celestial object. By reducing unnecessary lighting, we can help our invertebrate neighbors, including not only moths, but other nocturnal animals, such as Colorado fireflies, in maintaining their natural behaviors. It is important to view moths, with compassion, recognizing the vital role they play in our ecosystem. As Miller moths flutter through Colorado this year, try to approach them with curiosity and acknowledge their importance in maintaining our natural world. By valuing these creatures and implementing small changes, such as reducing unnecessary outdoor lighting, we can coexist.  By educating ourselves and attempting to understand and protect these often-overlooked creatures, we contribute to the preservation of our environment.

As with all invertebrates, moths are understudied, underappreciated and misunderstood.

Butterfly Pavilion is a leader in pollinator protection and conservation, including creating pollinator habitat, conducting research, leading conservation programs and community science volunteer opportunities.

Learn more about invertebrates and pollinators at butterflies.org