Late summer is a busy time for many arthropods – pollinators are busy taking advantage of late-season flowers, spiders are finding places to stash their egg sacs before freezing temperatures set in, and damselflies are mating and laying eggs that will overwinter under the snow. What interesting bugs and behaviors are you seeing?
Submit your bug pictures to bugid@missoulabutterflyhouse.org (and remember to include your name, the date, and the location where you took the photo)!
Header photo: We featured a Nordmann’s Orbweaver (Araneus nordmanni) back in August, but the striking coloration of this individual was too beautiful not to share. This large orbweaver is found throughout western North America and the northeastern United States, and has also been observed across Europe and Asia, but is largely absent from the Great Plains – likely because it prefers forested habitats. Its underside is flashy, perhaps as an attempt to startle predators, but the top of its body blends perfectly with the bark of the trees it uses to anchor its web. When threatened, it retreats to the tree trunk and disappears against the bark. – Klara Briknarova, August 28, 2025, Pattee Canyon, Missoula, MT
Obtuse Long-horned Beetle
Monochamus obtusus
Although it can be difficult to distinguish among a few very similar species of pine sawyer beetles (genus Monochamus), the stout elytra and black-red-black coloring on this individual’s thorax lead us to believe this might be M. obtusus. Pine sawyers are named for the loud, saw-like sound made by larvae while they are feeding. These beetles inhabit pine forests across North America; their slow-growing larvae (often taking two years to complete their lifecycle) eat their way through damaged pine, spruce, and fir trees, creating extensive, winding galleries. The adults are attracted to the scent of asphalt, as its chemical composition is similar to the compounds released by dead and dying coniferous trees. The male’s antennae can reach up to twice their body length and help them efficiently track down a mate.
Lisa Cloo, September 1, 2025, Turah, MT
Fierce Orbweaver
Araneus saevus
This orbweaver is fierce in name only (and maybe appearance, if you’re a bug). Like all North American orbweavers, this species is harmless to humans. It is found throughout northern and central North America, although it is largely absent from the Great Plains. Usually, it spins a web out from the side of a tree, but this individual was walking across a rock field surrounding a high mountain lake. The light colored vertical dash on the front of the abdomen is diagnostic for this species.
Chad Moore, August 31, 2025, South of St. Regis, MT
Lyre-tipped Spreadwing
Lestes unguiculatus
The Lyre-tipped Spreadwing is a species of damselfly found zipping around ponds and slow-moving streams across north-central North America. The name comes from the unique lyre-shaped paraprocts or “claspers” on the end of the male’s abdomen. During mating, the male will clasp the female behind her head so the pair remain connected even in flight. If the female is receptive, she will lift her abdomen to connect with the male’s accessory genitalia, located just behind his thorax, and the pair wind up in a shape not dissimilar to a heart.
Connie Geiger, September 1, 2025, Helena, MT
October Thorn
Tetracis jubararia
This appropriately named autumn moth is on wing from mid-August to November. A western species, it is found from southern California to British Columbia, and east to Saskatchewan, central Colorado, and even Ontario. Not much information is available on its lifecycle, but the larvae can be found on multiple plant species, including Alnus (alders), Betula (birches), Cornus (dogwoods), Populus (poplars), and Ribes (currants).
Misty Nelson, September 1, 2025, south of St. Regis, MT
Shamrock Orbweaver
Araneus trifolium
The abdomens of Shamrock Orbweavers (Araneus trifolium) can range in color from dark red to orange, yellow, brown, green, or any color in between. The abdomen is smooth and round with numerous white spots on its back that distinguish it from other orbweaver species. Unlike other orbweavers that might make their circular web in the eaves of your garage, on your deck, or in some other secluded spot around your house, the Shamrock Orbweaver prefers open areas and makes its web in low bushes or grasses. It can be found across North America, from Alaska to Newfoundland and as far south as New Mexico.
Lisa Cloo, September 4, 2025, Marshall Mountain, Missoula, MT
Juba Skipper
Hesperia juba
The Juba Skipper (Hesperia juba) is common throughout the western United States and north into British Columbia. Its larvae feed on perennial bunchgrasses, while adults feed on flower nectar from a variety of sources. Males are territorial, perching on or near the ground in gullies and valley bottoms all day waiting for females. There are typically two flights a year, one in late spring and another in late summer/early autumn.
Connie Geiger, September 5, 2025, Helena, MT
Bald-faced Hornet
Dolichovespula maculata
Despite its common name, Dolichovespula maculata is a species of aerial yellowjacket, not a hornet. It is omnivorous and is even considered beneficial due to its predation of caterpillars, spiders, and – as in this photo – flies. However, don’t get too close to an active nest – colonies aggressively defend their home and can sting repeatedly. Individuals also have the unique ability to squirt or spray venom from their stinger into the eyes of nest intruders, causing immediate watering of the eyes and temporary blindness.
Steve Parker, September 5, 2025, Huson, MT
Nevada Tiger Moth
Apantesis nevadensis
There is only one generation per year of these striking tiger moths (tribe Arctiini), with the flashy adults taking wing in late summer. The larvae overwinter as early instars and begin emerging on warm sunny spring days. When they pupate, they wrap themselves in silken cocoons, sometimes adorned with gravel, dirt, twigs, and even their own bristly hairs.
Misty Nelson, September 5, 2025, Rocky Mountain Gardens, Missoula, MT
Locust Borer
Megacyllene robiniae
Originally hailing from the northeastern United States, this longhorn beetle (family Cerambycidae) has made its way west as its host plant, Black Locust (Robinia pseudoacacia), has been cultivated and used for landscaping purposes across North America. Both the insect and plant are now considered invasive in our area despite originating on the North American continent. The larvae feed on – and are considered serious pests of – Black Locust, while the adults feed on pollen, preferentially from goldenrods (Solidago spp.), where this individual was found.
Carolyn Taber, September 8, 2025, Rocky Mountain Gardens, Missoula, MT
Nearctic Bumble Bee
Bombus vancouverensis nearcticus
This subspecies of the Vancouver Bumble Bee was recently separated from the species Bombus bifarus, the Black-notched Bumble Bee. Bombus vancouverensis nearcticus is widespread across western Canada and the United States. The other subspecies, B. vancouverensis vancouverensis, is restricted to Vancouver Island in British Columbia and the San Juan Islands of Washington; it may wind up as its own species as research continues. Either way, they are relatively small bumble bees, with workers measuring only 8 to 14 mm. When they engage in “buzz pollination,” a specialty of bumble bees, they usually hang upside-down from the flower to help shake the pollen loose.
Misty Nelson, September 5, 2025, Rocky Mountain Gardens, Missoula, MT