A Multitude of Moths

When entomologist Kyle Johnson talks about moths in all their mind-boggling diversity, he can scarcely contain his excitement.

“There’s such variety in terms of the shape, size, color, and form,” he says. “Size-wise, some are much smaller than a grain of rice, little specks you can barely see. And they range all the way up to the huge cecropia moth and the black witch, which are both the size of a bat. In the tropics you get the white witch and the atlas moths, which are almost like a flying dinner plate.”

He describes the “elegant tails” of attention-getting species like the luna moth, then veers off into wonder at “micro moths” that are “like a dandelion seed floating in the air,” with “wings that look like bird feathers.”

“Like a lot of small things, if they were magnified and people knew what they looked like, they’d be amazed—it’s such an alien world.”

Johnson, who has been a moth enthusiast since he was five years old, now applies that enthusiasm to his role for the Minnesota Department of Natural Resources’ Minnesota Biological Survey, where he keeps tabs on invertebrates, particularly moths. Lately, he’s been leading an ambitious project he’s long dreamed of: building a comprehensive list of all of Minnesota’s moth species. It’s the first of its kind.

The project, funded by the Legislative-Citizen Commission on Minnesota Resources, was approved in 2024 and will be complete by spring 2027. But it’s been on Johnson’s mind for at least a couple of decades, when he first became aware of the “hole of information about moths.”

Some Questions Aren’t Simple. In an age of voice-activated assistants and with high-tech devices in nearly every hand, it’s easy to presume that every basic factual question has been answered. “How many types of moths are found in Minnesota?” may seem like a straightforward query, but the answer is elusive.

While there is a comprehensive checklist for all the birds recorded in Minnesota (453 species) and a recent one for bees (508 species), no such checklist yet exists for moths—an order of insects, Lepidoptera, that includes butterflies.

Past work by the Minnesota Biological Survey has documented 1,940 moth species in the state, but that’s not seen as a comprehensive figure, and the new checklist will easily exceed that number. Johnson, who’s perhaps in a better position than anyone to hazard a guess, says Minnesota “has a conservative, low-end estimate of 2,500 moth species” and that the checklist could eventually reach 3,000 someday.

Building on his own impressive experience and fieldwork, but also that of several other moth researchers, plus museum collections, the project is “an effort from many people,” Johnson says.

Move Over, Butterflies. While butterflies, the best-known group of moths, get lots of press and attention from gardeners, native landscapers, and the general public, they are a relatively small part of the moth world. North America is home to perhaps 800 species of butterflies, compared to around 13,000 other kinds of moths. In Minnesota, the ratio is similar: For every given butterfly species, there are perhaps 15 species of other moths.

Johnson’s personal Lepidoptera tally is a whopping 2,000 species documented, including some recorded in the state for the first time—and he’s continuously adding to the total as he analyzes a backlog of specimens from past seasons. 

To Johnson, that’s the fun part. “There’s so much out there to discover, you’re not going to run out of things to find. That’s what makes a group like moths so exciting.”

The Night Shift. Finding and documenting thousands of moths takes ingenuity, persistence, and a lot of night work, since that’s when most moths are active. Johnson’s main survey technique is a white sheet illuminated by ultraviolet lights—a method that many amateur “mothers,” as they’re known, use to attract their quarry. 

He also uses traps that are essentially a bucket topped by a light and a funnel that guides moths down into a holding container. “It’s the sheet idea wrapped up into a trap,” he says. This setup enables him to survey remote or difficult habitats and to set up traps in multiple places on a single night.

Other methods involve luring moths with scents: pheromone traps and rotten banana–brown sugar bait. Johnson paints this sticky-sweet concoction on trees and shrubs to attract species that normally feed on things like flower nectar and tree sap.

Sometimes he’s just out at night with a headlamp, checking flowers or netting species that don’t come to light or bait well. In addition to all this nocturnal fieldwork, Johnson often does diurnal—daytime—surveys for day-flying moths.

Why Moths Matter. Let’s be real: When most folks think of moths, they probably think of ruined sweaters, spoiled cereals, or damage to their prized tomatoes. While a handful of moth species are pests, adult moths are remarkable for how harmless they are. Adult moths typically can’t bite or sting, and they don’t transmit human diseases. A small fraction of moth caterpillars can sting if handled, but nearly all are harmless and usually go unnoticed.

Besides, moths bring many benefits that you may not know about. “First and foremost,” Johnson says, “they are the dominant herbivores in the ecosystem on the order level.” By eating a lot of plants, and then being eaten by other living things, “they basically take that energy and move it up the food chain,” he explains. Moth eaters include spiders, birds, bats, and even big creatures like grizzly bears, which can put on weight eating moths.

And while many people are wise to the pollination services of butterflies, “Pollination does not stop after the sun goes down,” Johnson points out. “Moths are very important pollinators.”

Moths are valuable as indicator species, too, signifying ecosystem health through their presence or absence. “They can tell you a lot about habitat quality and land management,” Johnson says. “Some might be sensitive to pesticides and other pollutants, and that’s why we’re not finding them in certain areas. They’re also indicators of climate change.”

A List for Many. Johnson sees the moth checklist appealing to many different groups of Minnesotans, from academics and land managers to moth enthusiasts and “the general public with an interest in natural history.”

For natural resource managers, simply knowing which species are present in the state will have significant conservation value for preserving biodiversity, he explains, and the checklist may help “produce a candidate list of flagged species for future research and monitoring.”

For amateur moth watchers, the checklist can also help provide another entry point to the amazing world of Minnesota moths.

Getting the Data on Insect Decline. Insect populations seem to be declining globally, and moths are not immune to the trend. “The general consensus is that things are in a downward trend overall,” Johnson says. “That unfortunately seems to be the case, but it’s really difficult to quantify.”

On the positive side, Johnson says he is sometimes pleasantly surprised when he goes mothing in nighttime surveys. “There still are places, in the wildest landscapes of the north—Lake of the Woods or Koochiching counties—where you can have a night in late June and there’s over 200 moths on the sheet. It’s just dark with insect biomass.”

On other nights, especially when surveying in more fragmented landscapes in the prairie region or the metropolitan Twin Cities area, Johnson sees cause for concern.

“You think you have perfect weather, but the reaction is, Oh, that’s not a lot. That doesn’t feel right.”

These are just anecdotal observations, Johnson cautions, which is one more reason for solid data collection and analysis. “The important part of surveys like this is getting the precise data,” he says.

How to Help Moths. Anyone can help moths and other insects. Johnson’s basic advice is simple: Start by “paying attention to what’s around you.” Wherever you are in Minnesota, observe your surroundings and keep an eye out for moths, even if it’s just a few found at your porch light. Taking a photo and submitting it to a nature-sharing website is a real contribution to science.

And from there, if you’re comfortable, you can branch out by setting up a moth sheet or connecting with other people in the hobby. Consider participating in a “bioblitz,” where scientists and community members document species in an area in a single day, or check out an after-dark moth event at a park or nature center. Such efforts “build community, help you learn, reach out, and meet people,” Johnson notes. To really make an impact, Johnson urges fostering “a love and curiosity for natural history in society.”

Small, simple changes on a personal level can make a difference too, Johnson says. By “using fewer pesticides and herbicides, planting native plants, or creating native pollinator gardens,” the average person can help Minnesota insects and maybe even enhance their own health and happiness.

Getting to know your nocturnal neighbors, and appreciating them, might just be the first step to protecting them for the future.

Printed and online resources can help enthusiasts identify moth species. A notable new guidebook is Moths and Caterpillars of Minnesota, Wisconsin, and Michigan by Jim Sogaard. (Photos from the book, by Duluth-based photographer Sparky Stensaas, grace these pages.) Other guides to consult include the Peterson Field Guide to Moths of Northeastern North America and John Himmelman’s insightful and often hilarious Discovering Moths: Nighttime Jewels in Your Own Backyard.

In the online realm, Johnson cites free community-science sites such as iNaturalist.org and BugGuide.net as resources for identifying moth species, documenting sightings, and connecting with other moth-curious people. While community-focused, these sites are also popular with experts because they capitalize on an audience of observant, smartphone-wielding users who dutifully log their observations—even if they aren’t always quite sure what they’ve spotted. After all, there are far more regular folks who are nature spotters than there are scientists, and all those “What is that?!” observations can be useful.

In fact, Johnson plans to pull data from those crowd-sourced platforms in compiling the new checklist.

An Evolving List. The forthcoming Minnesota moth checklist by its nature won’t be written in stone. It will constantly evolve.

Johnson says the goal of the project is to “produce the first preliminary checklist.” Once new discoveries are made, the list will be updated and the original list will essentially be obsolete, but that’s the point. The idea is “to get people excited and build on it,” eventually creating a version two and, with each iteration, a clearer picture of Minnesota’s incredible and numerous moths.

“Even when this is done,” he says, “there’s still so much to discover out there.” 

Butterfly or Moth?

In everyday parlance, we talk about butterflies and moths as if they were separate groups of insects, but as DNR entomologist Kyle Johnson likes to remind people, “Fun fact, butterflies are a group of moths.” They all belong to the insect order Lepidoptera, which means “scale winged,” as they are covered in microscopic, plate-like scales. Family tree aside, the moths we know as butterflies share some general characteristics that can be used to tell them from other moths in Minnesota:

Butterflies

• tend to be larger (compared to the average moth)

• have clubbed antennae

• are more colorful

• fly primarily during the day

Moths

• are smaller than your average butterfly

• often (but not always!) have camouflage-like coloration that enables them to blend in and evade predators

• are more active at night

Johnson notes that there are many exceptions to these rules. "There are lots of day-flying moths," he says, such as hummingbird moths, as well as large, colorful moths like the cecropia.

How to Moth
Attracting moths and other bugs can be as easy as leaving the porch light on and seeing what shows up. But if you want to go a bit further, hang up an old white bedsheet and point a cheap black light at it. This setup will really put out a welcome mat—erm, sheet—for moths and other nocturnal insects.

The best part about putting up a moth sheet is that it gives you a good chance to see usually reclusive insects up close. Sometimes the critters that show up are small, so a hand lens or a macro lens attached to a phone is a great option. And don’t forget to check out the nooks and crannies of the sheet, around the light, and any nearby surfaces (walls, the ground, etc.), as moths, beetles, flies, and even spiders will often make an appearance. A headlamp comes in quite handy, too. Sometimes, the visitors might be unexpected, like the toads who happily line up for the bug buffet at some northern Minnesota blacklight sessions.

If you’re a bit bug-phobic, a few pro tips: Avoid getting too close to the light source, as many bugs will be drawn to it, and some might be fluttering around it. Wear dark clothes; that way you won’t be mistaken as part of the sheet.

While mothing, keep safety, and your neighbors, in mind: Don’t allow the light to contact the sheet or anything flammable, and keep your moth light from shining at surrounding homes. UV-safe glasses aren’t a bad idea, either.

So why are moths attracted to light, anyway? According to a study published in Nature, it likely has to do with the way they orient themselves spatially. Called the dorsal light response, it ensures that moths stay “right side up.”

It works like this: In the absence of light pollution, the sky is the brightest light source at night. Moths and other insects orient themselves toward it, with their back facing up. This enables them to fly level and essentially know where the ground is. When they encounter an artificial light source, they again turn their back to the light. Because artificial light sources can be pointed down or up or reflected at an angle, this can cause moths to become disoriented and circle the light source, stall out, or even flip upside down. Fully disoriented in the artificial light, many moths and other insects simply stay put, making it easier to observe them.