The miller moth is hard to love, but it deserves our respect

Every summer, the migration of the small insect plays a role in the food web. Don’t be annoyed when they show up in your bedroom.
According to multiple entomologists, the army cutwood deserves our sympathy. Whitney Cranshaw, Colorado State University, Bugwood.org

This article was originally featured on High Country News.

The seasonal miller moth migration had started. By late May in Colorado, Google searches for “get rid of moths” left orbit. Over a group chat, I asked friends how they were handling this seasonal visitor. “I find miller moths in my closet, my bathroom, and sometimes in my bed. I get a washcloth and wet the tip—my moth katana—and twirl that sucker for the nightly harvest,” said Jack Martin. “My wife left me to join the miller moth migration,” joked Sam Krason, while Connor Rafferty, a graphic designer, offered a vivid tableau. “Every time I open my garage door, I have to wait a minute for the trail of moths to exit the garage, like a bunch of bats out of a cave, before I can walk in.”

After a wet winter, moths the size of dollar coins and the color of dehydrated mulch cascade onto Wyoming, Colorado and New Mexico from their nesting sites in the High Plains. Beginning with the June migration, the miller, or army cutworm moth, touches nearly every denizen in the region—their faces, their pillows, their window panes—but rarely their hearts. Because the miller finds refuge in dark crevices to during its journey to the Rocky Mountains to pollinate flowers, it often ends up in garages and bedrooms instead. Trapped and disoriented, the moth panics. Frantic attempts by the resident hominids to swat the confused insect are frustrated by its evasive acrobatics around the nearest light source, which, to the insect, resembles the moon it navigates by. Neither the manic wing-flapping nor the buildup of tiny gray corpses inside homes has done much to endear the species to residents. But according to multiple entomologists, the diminutive creature deserves our sympathy. 

“They’re not exactly intelligent, but they’re doing the best they can,” said Maia Holmes, a Colorado State University entomologist. “So, when you find them ramming themselves up against your window at a time or place you don’t want them, they’re just lost and confused.” Even though the miller moth aggravates human beings, flowering plants and other animals delight in its arrival. The army cutworm begins life as a green-striped caterpillar munching on grasslands and fields at lower elevations. In late spring, it pupates into a winged adult and chases wildflowers up into the Rocky Mountains, where it spends the summer. Along the way, the moths become a crucial food source for native bird species and bats—even grizzly bears in Yellowstone National Park that turn over logs and gorge on the sheltering arthropods. 

As industrial agriculture transformed the landscape of the West in the late 1800s, the human relationship to native insects changed, too. “Historically speaking, the moth wasn’t a problem,” said Holmes. “Then we start growing a lot of corn and wheat for money. Army cutworms were like, ‘Great, there’s more food.’ But humans were like, ‘Wait a minute, we use these crops for money.’” An all-out war on the army cutworm had ensued by the late 19th century, buoyed by an emerging school of thought known as “economic entomology.” This approach to insect management, backed by the U.S. Department of Agriculture, sought to safeguard agricultural profits against its non-human competitors. Controlling cutworms and other “pests” required researching their life cycle and led to USDA officials evaluating pesticides and spreading anti-insect propaganda that reads almost like medieval folklore. 

In 1919, a Colorado newspaper published an ominous USDA press release titled “Cutworm Cowardly Rascal,” warning readers that the cutworm “watches and waits … then sneaks out in the night to destroy the plants.” A year later, an experimental farm operated by the Great Western Sugar Company in Longmont, Colorado, released its own study: The Principle Insect Enemies of the Sugar Beet. Liberally footnoted with USDA research and targeted at numerous arthropods, the study saved its most unhinged descriptions for the Miller:

“Like the evil gnomes of old who sallied forth on moonless nights to wreak vengeance upon some hapless wayfarer, the cutworms come forth from hiding and under cover of darkness, despoil the farmers’ crops.”

The farmers didn’t realize that monoculture crop fields automatically attracted miller moths accustomed to scanning biodiverse grasslands for food. Faced with fast-adapting insects like the army cutworm, the industry embraced chemical weapons to protect crops. “If your primary aim is short-term economic efficiency, the strongest, most powerful and most immediately effective chemicals are the logical endpoint,” said Texas State professor James McWilliams, author of American Pests: The Losing War on Insects from Colonial Times to DDT. “It’s really quite amazing,” McWilliams said. “You can look at economic entomology before 1960, and there’s just no consideration at all of long-term environmental impacts.” 

Application of the deadliest pesticides like DDT only abated in the 1960s, after harrowing revelations concerning their environmental consequences emerged in Rachel Carson’s Silent Spring. But changing our cultural attitudes toward insects has proven to be a much slower process. In fact, the name “miller moth” is a linguistic artifact left over from the era of ecocidal excess. The term is generic, referring to any moth deemed a pest, whether in Louisiana or the Rocky Mountain West. 

But more recently, Moussa Diawara, an entomologist at CSU Pueblo, has been encouraged by the ethos of tolerance he’s observed in students, and by the calls he’s begun receiving from the public. “I used to get a lot of calls about how to get rid of miller moths. That has come down a lotEven in my classes, students are more aware of the importance of biodiversity. So the public perception is changing, but slowly,” Diawara said.

Samuel Shaw is an editorial intern for High Country News based in the Colorado Front Range. Email him at samuel.shaw@hcn.org or submit a letter to the editor. See our letters to the editor policy. Follow Samuel on Instagram @youngandforgettable.