Happy Friday the 13th! While many regard today as an omen of ill fortune, we consider ourselves pretty lucky with the arthropod diversity on display this week. The hustle and bustle period of insect activity may be waning, but there’s still plenty to get out and observe before we meet the first frost.
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: Alder Flea Beetle (Altica ambiens). Klara Briknarova, September 9th, 2024. Maclay Flat, Missoula, MT.
California Tortoiseshell
Nymphalis californica
California, Compton, and Milbert’s Tortoishells can be found in our area and are generally smaller than the Mourning Cloak. The California’s brightly colored dorsal (upper) side of the wings is opposite to their ventral (under) side, which looks more like a dead leaf. The ventral side can look similar to a Comma’s but they lack the white “comma” on the hindwing or the sharp “ins and outs” along the wing edges. Caterpillars feed on various species of wild lilac (Ceanothus). California tortoiseshells stick mainly to the west, but sometimes stray to the midwest and east after population irruptions.
Kamal Fox, September 1st, 2024. Seeley Lake, MT.
Stealthy Ground Spider
Family Gnaphosidae
Stealthy ground spiders are a large family of cosmopolitan spiders with over 2,000 described species. The most well-known genus in this large family is the ant-mimicking Micaria, whose cryptic appearance and behavior lend them the nickname “ant spiders.” Ground spiders are active predators, opting to chase down their prey instead of utilizing a web. While many spiders pursue small prey (at least, smaller than they are), stealthy ground spiders are bold, attacking prey that is both larger and potentially more dangerous than themselves. Instead of utilizing slow-acting venom to subdue their catch, they produce thick, gluey silk from their spinnerets and swath their prey, often securing their mouths and legs first.
Klara Briknarova, September 4th, 2024. Missoula, MT.
Pearly-winged Lichen Moth
Crambidia casta
Moths are often named for traits exhibited by their adult form OR their larval form – but rarely both. The pearly-winged lichen moth is an exception. Its name comes from the pearly white forewings of the adult, and their larval food source – lichens. They are found in the northern United States and southern to central Canada in dry, open woodlands and prairie riparian areas.
Lisa Cloo, September 5th, 2024. Turah, MT.
Cabbage White
Pieris rapae
This cosmopolitan butterfly is a prolific breeder, which explains why its range covers most of North America since its accidental introduction in the 1860s. The caterpillars, also known as the “imported cabbageworm,” have a mighty appetite for cruciform vegetables like kale, broccoli, and of course, cabbage. Currently, South America and Antarctica are the only continents without a cabbage white population.
Dylan Spradlin, September 3rd, 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 (the food source for their beautiful caterpillars, shown here). 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.
Ramona Grey, September 6th, 2024. Missoula, MT.
Cream-spotted Ladybird
Calvia quatuordecimguttata
Despite its name, the cream-spotted lady beetle comes in a wide variety of color morphs, including the form seen here with large black spots. The name stems from the Eurasian color morph, which exhibits – you guessed it – cream-colored spots. This species is widespread across Europe and Asia, and is an introduced species to North America.
JH, September 11th, 2024. Spokane Creek, Helena, MT.
Tall Flea Beetle
Disonycha procera
Flea beetles are so named for their enlarged hind femora, which allows them to jump – like a flea. We’re stumped as to why this species is called the “tall” flea beetle; it is larger than most at about 6mm long. Tall, though? Not the first word that comes to mind. Flea beetles are leaf skeletonizers, eating the outer layers of leaves and leaving a decimated “skeleton” behind. While some species are considered pests, many are used as noxious weed control.
Klara Briknarova, September 9th, 2024. Maclay Flat, Missoula, MT.
Banded Garden Spider
Argiope trifasciata
Female orbweavers like this stunning banded garden spider construct the familiar, intricate webs we see in the fall to ensnare their insect prey. Many species in the genus Argiope will add “decorations” to their webs; the various designs change depending on the species. These decorations are known as “stabilimentum,” and the jury is out on their exact function. You’ll find banded garden spiders in open places with tall grasses or shrubs across southern Canada and throughout the U.S. (and many other countries around the world).
Owen Quinn, September 8th, 2024. Missoula, MT.
Locust Borer
Megacyllene robiniae
Originally hailing from the northeast United States, the locust borer 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 take nectar, preferentially from goldenrod (where this one was found).
Ashley Mattson, September 10th, 2024. Missoula, MT.
Knapweed Root Moth
Agapeta zoegana
These distinct, bright yellow moths are native to Eurasia but were introduced to the US in 1984 as a form of biocontrol in the fight against knapweed. They are found in most northwestern states where knapweed has established. Adults live for up to two weeks, with females laying up to 80 eggs on knapweed plants. The emerging larvae will bore into the roots of the plant, causing moderate damage. They are not known to case damage to other plants.
Klara Briknarova, September 9th, 2024. Missoula, MT.
