25 Sep A Soft-Winged World

What do moths have to do with owls? Just ask Mat Seidensticker. After nearly a decade spent studying owls across Montana and Alaska, Seidensticker focused his research on the flammulated owl, one of Montana’s smallest and most cryptic species. Soon, it became impossible for him to ignore the moths — insects that this owl hunts extensively during the summer.

NEVADA TIGER MOTH (Apantesis nevadensis)

In 2015, Seidensticker began working with other researchers at the Bitterroot Valley’s MPG Ranch, studying not only small owls, but also nighthawks and poorwills. And, once again, the moths kept fluttering into his life. Eventually, they would show him they were far more important than most people imagine.

Now, over 30,000 moth specimens later, Seidensticker and the initiative he founded, the Montana Moth Project, along with his collaborators, Chuck Harp and Marian Kirst, have learned a great deal about the roles that moths play in nature. These soft-winged aerialists feed a wide variety of animals, shape plant communities profoundly, and carry far more pollen than anyone would have guessed.

To Seidensticker, the night sky is like an ocean. Moths, flying ants, and crane flies are “sky plankton,” a teeming community of aerial life that feeds the larger creatures. Common nighthawks are the “whales of the sky,” dipping and darting over the sunset as they scoop up moths with their gaping mouths.

The author follows Seidensticker as he carries a bucket trap into the forest.

On a late August evening near Helena, we don’t have to look far to spot the nighthawks skimming through the air high above us as they hunt for dinner. Tonight, we’re hunting moths, too. Photographer Lea Frye and I have joined Seidensticker for one of his nocturnal expeditions as he works methodically to document Montana’s moths.

A swath of dark gray clouds skids over the mountains as Seidensticker hangs a white sheet between two aluminum poles. This unusual-looking device is a “light sheet,” one of the common methods moth researchers use to study these elusive fliers. Seidensticker fires up a generator as darkness approaches, powering a black light and mercury vapor bulb mounted next to the sheet. The lights will confuse nearby moths as they navigate through the night, throwing off their sense of up and down. The white sheet will give them a place to land while we identify them.

Seidensticker carefully installs the bucket trap, a homemade moth collector involving a battery, black light, funnel, and 5-gallon bucket.

“It looks like we’re setting up a small drive-in movie theater,” I observe.

“We are!” Frye says.

Tonight’s outdoor theater is at the knees of the mountains, where the grassland shifts into pine forest and the conifers begin their march up toward the Continental Divide. We’ve already set up several bucket traps — homemade moth collectors involving a battery, black light, funnel, and 5-gallon bucket — among patches of different vegetation deeper in the forest. With luck, the buckets and the sheet will show us a great variety of moths.

The light sheet is a glowing attractant on a cloudy August night.

Everything is in place now. The ponderosa pines are majestic black silhouettes behind us, and a quarter moon is sailing through the southwestern sky. Now, our only problem is the wind, which is proving more energetic than we’d hoped. It seems to be discouraging moth activity.

EMERALD (Geometrinae)

Gusts rattle the sheet, sigh through the pines, and rustle the aspen leaves. We wait, listening to the monotonous trill of the tree crickets filling the night. If only the wind would settle down.

At first, the moths trickle in one by one. Then, we get a lull in the wind, and they start arriving in fluttery waves: a small snapshot of the invisible nocturnal river of insects flowing through the dark skies around us. The diversity of colors and forms is stunning. There are the subtle ones, of course, well-camouflaged in a delicate palette of charcoals, grays, and browns, as if an artist sketched their wings. But not all of the moths blend in.

Several grass-veneers (Crambus) appear, sleek honey-colored moths with flashy white racing stripes. Frye finds an emerald (Geometrinae), its smooth green wings fringed and patterned with white. I’m fascinated by the sulfur knapweed moths (Agapeta zoegana), bright darts of yellow with a black chevron pattern crossing their wings. Several Nevada tiger moths (Apantesis nevadensis) clamber along the sheet, clothed in a mosaic of black and cream that resembles a Cubist painting. Their hindwings are unexpectedly salmon-colored.

The range of shapes and sizes is mind-boggling: from the tiny white speck of a micro moth, no larger than a midge, to broad-winged gray stealth fighters and furry-bodied Nevada tiger moths. And then there are their eyes, gleaming coppery, brassy, and purple in the intensity of the light. We go from moth to moth, taking photos as Seidensticker identifies the species, and a hundred tiny eyes shine back at us in the night.

Our luck doesn’t last long, though. Soon, the restless wind resumes billowing, and the moth activity slows down. By 11 p.m., we’ve packed up the light sheet and retired to our tents. Now, everything is riding on our three bucket traps, whose lights will continue shining until morning. With luck, the wind will quiet in the upcoming hours, facilitating a strong flight of moths and an abundant catch.

Two hours later, it’s not looking good. White flashes light up the turbulent sky as a thunderstorm plows over the Continental Divide, giving us a brief but thorough soaking. Each bucket trap is roofed with just a small aluminum pan. Is it enough to weather the storm?

Seidensticker and the author wait for moths to arrive at the light sheet.

The call of a Swainson’s thrush pierces the moist pre-dawn stillness as we open the first trap. Last night, we left it on a narrow ridge of Douglas fir trees, overlooking a drainage dotted with aspens and willows. Despite the midnight shower, the trap has served its purpose. Among the egg cartons inside, which provide places for moths to rest and hide, we see a rich assortment.

“Just looking at it here, there’s probably 20 to 30 species,” Seidensticker tells us. Some of these are new to me, including a broad-winged yellow moth. This one, like the pale green emerald we saw earlier, is a member of the geometer moth family, whose caterpillars are familiar to many people as inchworms.

Egg cartons provide safe places for moths to hide inside the bucket trap.

The second trap, on a lower slope with a mature aspen stand nearby, gives us the largest moth we’ve seen so far, a species of underwing (Catocala). This moth’s forewing is a fine achievement of camouflage, an intricate mottling of charcoal that resembles old aspen bark. But there’s nothing subtle about its hindwing, a visual exclamation declared in pink and black stripes.

We retrieve the third trap from our lowest-elevation site, not far from the previous night’s light sheet. Here, large granitic boulders tower up among mature ponderosa pines, and patches of grassland and antelope bitterbrush provide habitat not present on our other sites. What catches my eye in this trap are two magnificently large sphinx moths, robust and furry. One of them, which Seidensticker identifies as an eyed sphinx moth (Smerinthus), has a pink-blushed hindwing with a surreal blue eyespot. The other, a spurge hawk moth (Hyles euphorbiae), has a pleasing bronze stripe in the forewing and a fuchsia-hued underside. These are the only sphinx moths we’ve seen tonight, and I admire the family of accomplished hoverers that often resemble hummingbirds when they fly.

In the pre-dawn hours, the egg cartons reveal an assortment of moths.

Despite the uncertain weather, it’s been a productive night. Seidensticker estimates that we’ve caught between 100 and 150 species.

As amazing as the assortment is from our single night in the field, it’s just one piece in the larger puzzle that the Montana Moth Project is gradually assembling. Already, the project has documented a whopping 1,250 moth species in the state. And that’s just the macro moths — the larger-bodied species, relatively straightforward to recognize in the field. Then, there are the micro moths — tiny midge-sized specks, much more difficult to identify but nevertheless important in the ecosystem. In fact, Seidensticker says, the micro moths are estimated to be three or more times as diverse as the macros.

The Montana Moth Project is collecting scientific specimens of all these species. The specimens go to the C.P. Gillette Museum of Arthropod Diversity in Fort Collins, Colorado or to the California Academy of Sciences in San Francisco, where they’re carefully curated as a reference library for biodiversity. In time, all of them — even the tiniest moths — will be identified. Including the micros, Seidensticker predicts there could easily be over 4,000 species of moths in Montana.

UNDERWING (Catocala)

This number is mind-boggling — but what’s really incredible are the diverse lives of all these moths. Every species has its own story, a unique way of life fine-tuned to the harsh weather and varied vegetation of the Montana landscape. A lot of the details are still unknown; we’re still “in the dark” about many species’ basic biology. But what we do know is this: Moths are involved in a tapestry of relationships that is indispensable to the ecosystems around us.

According to Seidensticker, there’s an intimate “double link” between local moths and local plants. A tremendous variety of caterpillars chew on plants, forming the first link. Many adult moths feed on flower nectar, forming the second. Through these relationships, moths shape plant communities, feed a wide variety of animals, and contribute to pollination.

Caterpillar food plants, like the caterpillars themselves, are greatly varied. The pale enargia (Enargia decolor) develops primarily on aspens, tying the leaves together with silk. The oblique-striped emerald (Synchlora bistriaria) munches on sunflower and goldenrod blooms. Ambesa laetella, a beautifully patterned snout moth without a common name, feeds on wild roses. Eyed sphinx larvae rely on willows and cottonwoods. And through the simple act of chewing on leaves, caterpillars shape the course of evolution, pushing plants to develop defenses like hairy armors, bitter flavors, and aromatic compounds. Meanwhile, the host plants become caterpillar factories, producing millions of juicy larvae that songbirds eat.

If a caterpillar manages to escape the songbirds and transform into a winged adult, it may become important prey for flammulated owls or nighthawks. Bats feed so heavily on moths that certain moth species have developed sonic defenses, emitting high-frequency sounds that interfere with the bats’ sonar. Grizzly bears gorge on adult army cutworm moths, which spend the summer hiding in talus slopes in the mountains. These moths are more calorie-dense than butter.

Meanwhile, scientists have only recently begun to recognize how important moths can be for pollination. In 2020, Seidensticker and his colleagues did a pilot study in the Bitterroot Valley using DNA barcoding to identify pollen swabbed from moth mouthparts. Impressively, they found moths transporting pollen from nearly a hundred plant genera, including common groups such as asters, legumes, and currants, as well as rarer plants like orchids and catchflies.

Moths may be especially important in this way because of how far they can carry pollen. Indeed, some moth species have been documented carrying pollen hundreds of miles. With their long-distance flights, they can connect the genes of isolated patches of plants. Bees, on the other hand, tend to forage close to their nests.

As researchers like Seidensticker continue to learn more, it’s becoming clear that moths are amazingly diverse, awesomely complex, and critically important to life around us. For Seidensticker, his journey of discovery began with owls. Now, it’s a web of connections: these fluttery pollen carriers link grizzly bears, bats, birds of the night, and plants in a complex dance.

And there’s still so much to learn. By 2030, the Montana Moth Project expects to have a comprehensive inventory of moth species in Montana. In the next decade, they’ll focus on developing the seasonal picture of when these moths fly. From there, the sky’s the limit, with much more to learn about pollination, host plants, and food webs.

It’s a soft-winged world that most of us take for granted. But the moths are out there — fluttering through our gardens, soaring through the nighttime pines — waiting for us to notice them.

Shane Sater is a naturalist who has spent the last decade learning about the birds, plants, and insects of the northwestern United States. His writing blends science and art in celebration of the natural world around us. Find more of his work and listen to his podcasts at wildwithnature.com.

Helena, Montana photographer Lea Frye captures the essence of wild animals in their natural Rocky Mountain habitats. Her work brings to life the beauty and behaviors of wildlife, showcasing the landscapes they roam.