Happy National Moth Week! Every year, during the last full week in July, we celebrate the diversity and life histories of the Lepidopteran underdogs – moths! National Moth Week is a worldwide endeavor to expand public knowledge and awareness of these crucial pollinators. So this week, we’re taking a look at some of the local moths you can find around western Montana!
Forage Looper Moth
Caenurgina erechtea
The forage looper may look like a “typical drab moth,” but their larvae are easily identified and commonly known as “inchworms.” Part of the Looper subfamily (Plusiinae), the caterpillars lack two pairs of prolegs in the middle of their bodies. Without those fleshy foot-like organs, they move in a “looping motion,” inching their way along. Larvae feed on giant ragweed (Ambrosia trifida) and varieties of clover, grass, and alfalfa. Adults are on the wing from March to November (and personally, we don’t find them drab at all).
Klara Briknarova, July 15th, 2024. Missoula, MT.
Leafy Spurge Hawkmoth
Hyles euphorbiae
These large hawkmoths (sphinx moths) are a non-native species that were released in the fight against leafy spurge. As the first biological agent to combat leafy spurge, these moths have inhabited the United States since 1965. The caterpillars are striking, with colors ranging from vivid green and yellow to dark red, orange and grey, depending on the caterpillar’s age. As adult moths, their wingspan can reach close to 10 cm, and like many day-flying moths, are often mistaken for hummingbirds.
Nancy Hirschenberger, July 12th, 2024. Missoula, MT.
Police Car Moth
Gnophaela vermiculata
When visitors ask us how to differentiate moths from butterflies, we tell them that one of the general rules is “butterflies fly during the day, moths fly at night.” The police car moth is just one exception to this rule. This unique-looking (and uniquely named) moth ranges throughout the Rocky Mountain region of North America, as far north as British Columbia and south to New Mexico. They occupy mid-elevation habitats like mountain foothills and nectar from herbaceous flowers like thistle and goldenrod. Adults are on the wing briefly in late summer, typically July through August. The larvae – whose coloring changes as they grow and eventually matches the adults – hatch in the fall and overwinter in the ground.
Connie Geiger, July 24th, 2024. Helena, MT.
Small-eyed Sphinx
Paonias myops
Despite their name, this moth has average, moth-sized eyes; however, the eyespots on their hindwings are small compared to those of similar species. These gorgeous moths range throughout the US, southern Canada, and Northern Mexico. Caterpillars are voracious eaters of wild cherry, hawthorn, and other trees, but like many species of moths, after emerging from the cocoon, the adults lack functioning mouthparts and do not feed. Their adult lifespans are relatively short, as they are entirely reliant on fat reserves they built up as caterpillars.
Christian “The Butterfly Whisperer,” July 10th, 2024. Missoula, MT.
Sagebrush Girdle
Plataea trilinearia
The sagebrush girdle, presumably named for their suspected larval food source, Artemisia spp., is a widespread western moth species that prefers open, arid habitats like desert grasslands, sagebrush flats, and prairie badlands. Their bold wing patterns make them easily distinguishable from other species in the Plataea genus. The species experiences a single generation, even towards the southern states, and adults are commonly encountered in large numbers near lights in the spring.
Klara Briknarova, July 4th, 2024. Lamar Valley, Yellowstone National Park, MT.
Ranchman’s Tiger Moth
Arctia virginalis
This striking western moth was recently reclassified from the genus Platyperus into the genus Arctia, along with four other genera of moths. They are commonly found in riparian areas and wet lowland prairies and meadows, where their larvae feed on a variety of herbaceous plants. Their bold patterning makes adults readily identifiable, but the caterpillars are easily recognized, too: Their stout, fuzzy black and brown bodies and long, dense hairs make them an adorable find – you might know them as “woolly bears.”
Misty Nelson, June 28th, 2024. Erskine Fishing Access, Frenchtown, MT.
Delicate Cycnia Moth
Cycnia tenera
Like many species in the tiger moth subfamily (Arctiinae), these moths fly during the day and at night but are preferentially nocturnal. As night fliers, they have evolved an impressive defense against bats. Equipped with “ears” that are sensitive to the echolocation call frequencies used by bats, they listen for and jam the bat’s echolocation with ultrasonic clicks, throwing off the bats’ ability to accurately see the potential meal. Additionally, the moths are distasteful to birds, and evidence suggests bats don’t find them very tasty, either.
Klara Briknarova, July 10th, 2024. Rattlesnake Recreation Area, Missoula, MT.
Large Tabby
Aglossa pinguinalis
Aglossa pinguinalis‘ common name, the large tabby, evokes a pleasant image of a housecat and even features similar patterning, but this species goes by another common name: the grease moth. Their dark, indiscriminate larvae inhabit human or animal dwellings, taking up residence in cellars, barns, caves, or animal burrows. There, they bulk up on stored animal fats or dung, taking a full two years to complete their life cycle and overwintering in their larval stage. This species was introduced to North America around or before 1990, and little information is available on their biology and distribution.
Klara Briknarova, July 8th, 2024. Missoula, MT.
Spotted Thyris Moth
Thyris maculata
This minuscule (12-15 mm) moth is a tricky find; there are scattered records of this species in the west, but even in the east (where they are significantly more abundant), their size can make them easy to miss. If you’re lucky, you may find groups of them forming “puddle parties.” They belong to the family Thyrididae, the window-winged moths, and are a poorly understood group as a whole.
Klara Briknarova, July 10th, 2024. Rattlesnake Recreation Area, Missoula, MT.
Vagabond Sod Webworm Moth
Agriphila vulgivagellus
Also known as the “vagabond crambus,” this moth can be readily identified and placed in the family Crambidae, the crambid snout moths. Moths in the family Crambidae typically feature a long, fuzzy, snout-like appendage, and while the family name personally evokes an image of the central European folk legend Krampus, the name Crambus is derived from Greek and means “dry or parched.” They are commonly found in grasslands and fields, where their larvae feed on wheat, rye, and other grains. Adults are on the wing from August to October, and, like many nocturnal moths, are attracted to lights.
Connie Geiger, July 17th, 2024. Helena, MT.
