Category Archives: Insects

Brown marmorated stink bug (Halyomorpha halys)

Photo by Alfredo Colon

Brown marmorated stink bug (Halyomorpha halys) is an exotic, invasive, true bug. It is native to China, Japan, Korea, and Taiwan. It was accidentally imported into the United States, probably in shipping crates or on machinery. It was first collected in Allentown, Pennsylvania in September 1998, but by then there had already been several sightings. Since its introduction in the U.S., the brown marmorated stink bug has spread rapidly. It now occurs in the east from Maine to Minnesota, south to Florida and eastern Texas, and in the west from northern Washington to southern California. Between these areas there are many scattered sightings and a few expanding populations around the larger metropolitan areas.

Brown marmorated stink bug is a voracious eater. It damages fruits and vegetables, causing pitting or scarring on the outer surfaces. It also damages ornamental crops, causing small, ⅛″ (4 mm) in diameter stippled areas around feeding sites. It is considered an agricultural pest. It feeds on and causes damage to a wide variety of crops, including apples, apricots, Asian pears, cherries, corn (field and sweet), grapes, lima beans, nectarines and peaches, peppers, tomatoes and soybeans. The wounds it creates can be an entryway for diseases to attack the plant.

Brown marmorated stink bug is also a nuisance to humans. In early fall, it begins looking for a place to spend the winter. It frequently finds its way into people’s houses. Often, an individual is found near a window or door, which is its original entry point. Large congregations may be found hiding under furniture like bookcases, beds, or sofas, or under or behind baseboards.

Adults are variable in size, ½″ to ⅝″ (12 to 17 mm) in length. The body appears broad-shouldered and somewhat shield shaped. The color is also variable, usually brownish gray but sometimes brownish yellow, grayish brownish-yellow, orangish brown, or chestnut brown. The entire body is densely covered with tiny dark pits.

Emerald ash borer quarantined in Minnesota

emerald ash borer
Photo by Babette Kis

On November 1, 2023, the Minnesota Department of Agriculture declared a quarantine to prevent the further spread of emerald ash borer. It prohibits the importation of firewood and other regulated articles into the state, and the movement of those articles from quarantined areas to uninfected areas.

Emerald ash borer, also known by the acronym EAB, is an exotic, invasive, small to medium-sized, metallic wood-boring beetle. It is native to northeastern Asia, including China, Mongolia, North and South Korea, Japan, Taiwan, and far eastern Russia.

Emerald ash borer was first detected in North America in 2002 in Detroit Michigan. It was probably imported in the wood of a shipping crate in the late 1990s. It has spread rapidly since its introduction. It now occurs from Maine to northern Georgia, west to Minnesota and northeastern Texas. It was discovered for the first time in Minnesota on May 14, 2009, in South Saint Anthony Park in St. Paul. It is now common in southeastern Minnesota, and it is continuing to spread in the state.

Emerald ash borer larvae feed exclusively on black ash, green ash, and white ash. They feed on the inner bark (cambium), creating serpentine tunnels (galleries) that interrupt the flow of food. They eventually girdle and kill the branch or tree. They have killed millions of trees in the eastern United States, including over five million trees in a 3,000 square mile area of Michigan.

Adults are active in Minnesota from May 1 through September 30. They are found in deciduous forests and woodlands, in parks, and in urban and residential areas, anywhere ash trees are found.

On October 8, 2003, the USDA Forest Service imposed a quarantine on emerald ash borer. It prohibited the interstate movement of all firewood and other regulated items out of infected areas. The USDA removed the quarantine effective January 14, 2021. An emerald ash borer female can fly up to 100 miles in her lifetime. The quarantine had not been effective in preventing the spread of the beetle into adjacent areas.

The Minnesota Department of Natural Resources estimates that there are nearly a billion ash trees in the state. Infected forests dominated by black ash will become grasslands, brushlands, or marshes. City budgets will be strained by the costs of removing dead trees from their streets.

The Minnesota quarantine will remain in effect until cancelled.

Ailanthus webworm moth (Atteva aurea)

Ailanthus webworm moth
Photo by Babette Kis

Ailanthus webworm moth (Atteva aurea) is a small, native, ermine moth with a colorful appearance and an unusual history. It was formerly native to the tropical Americas, including southern Florida, Central America, and the Caribbean, where its larval hosts were paradise tree (Simarouba glauca) and Simarouba amara. In 1784, the Chinese tree of heaven was introduced into Philadelphia. The tree was fast growing and spread quickly. When it reached Florida in the 1850s, ailanthus webworm moth found it to be an acceptable host. The moths then began moving north to wherever their new host was found.

Ailanthus webworm now occurs throughout the United States east of the Great Plains, and in southern Quebec and Ontario Canada. It is common in the eastern United States, uncommon but increasing in Minnesota. Tree of heaven, which is often planted as an ornamental in urban areas, remains the primary larval host, but larvae have also been found on avocado, Emory’s crucifixion-thorn, and sumac. Adults are found visiting flowers from May to October in Minnesota. They can’t survive northern winters, but they recolonize the northern range of tree of heaven every year. Although its range has recently expanded greatly, ailanthus webworm moth is not considered invasive by any state or province.

Adults are 7⁄16″ to ⅝″ in length and have a 11⁄16″ to 13⁄16″ wingspan. The forewings are reddish-orange with four broad black bands filled with white or pale yellow spots of varying size. The bright pattern is thought to be a warning to predators of their unpalatability. The black areas have bluish-purple reflections. The hindwings are mostly translucent with black on the margins and black veins.

Horned spanworm moth (Nematocampa resistaria)

Horned spanworm moth
Photo by Babette Kis

Horned spanworm moth (Nematocampa resistaria) is a small geometer moth. It occurs across the United States and southern Canada. In the U.S. it is common east of the Great Plains and in the northwest but is rare or absent elsewhere. Adults are found from early June to late September in deciduous and mixed forests and woodlands, in meadows, and in parks.

Female forewings are whitish or cream-colored with reddish-brown lines and veins, numerous short horizontal lines, and a purplish-brown patch on the inner half of the wingtip. The hindwing is similar, but the entire tip of the wing is dark. The male is similar but smaller, is usually yellowish, and there is a dark brown blotch at the tip of the wing.

The adult sometimes rests on the upper side of a leaf, where it resembles a dead leaf; on the underside of a leaf, where it resembles a dead patch; or on leaf litter on the ground, where it blends in with the background.

Horned spanworm moth
Photo by Alfredo Colon

The caterpillar is up to ¾″ long and is instantly recognizable. The ground color varies from yellow to brown and is heavily mottled with brown. On each of the first and second abdominal segments there is a pair of curled, extendable, white-tipped tentacles (filaments).

The caterpillar often rests on an upper leaf surface with the body looped. It has been suggested that this mimics a fallen flower and its stamens. When alarmed, it inflates the filaments to twice their length.

Meal moth (Pyralis farinalis)

meal moth
Photo by Mike Poeppe

Meal moth (Pyralis farinalis) is a small, broad-winged, triangular moth. It is cosmopolitan, occurring around the world, but is most common in Europe and the United States. It is found anywhere grain is processed or stored, including warehouses, barns, and most home pantries. It is not the only moth common to home pantries, nor is it the most common. That distinction belongs to Indian meal moth. Other common pantry moths are Mediterranean flour moth, brown house moth, and white shouldered house moth.

Meal moth larva feed on cereals (plants in the grass family), grains (edible seeds of cereals), and vegetables, including potatoes. Adults do not feed and are short-lived. They mate as soon as possible after emerging, then die after nine or ten days. They rest with their wings spread wide, their abdomen raised at a right angle to the body, and their antennae folded back over the body.

Chinese mantis (Tenodera sinensis sinensis)

Chinese mantis
Photo by Corey Anderson

There are only two species of praying mantis in Minnesota, Chinese mantis and European mantis. Neither is native to North America. The most common by far is Chinese mantis (Tenodera sinensis sinensis). It is native to Japan, China, North and South Korea, Thailand, and Micronesia. It was accidentally introduced in Philadelphia in 1896. It is now common in the United States and southern Canada east of the Great Plains, in California west of the Rocky Mountains, and in most of Asia. It is uncommon in the southern third of Minnesota, where it is at the northwestern extent of its range, and is absent from the remainder of the state. It is found in grasslands, meadows, agricultural fields, and woodlands, and at the sides of streams and rivers.

Chinese mantis are large predaceous insects. They eat anything they can catch, including insects, small amphibians and reptiles, and hummingbirds. They remain stationary with their legs raised up as they wait for prey. Though they have wings, females do not fly. Males can fly only short distances. Adults are active in summer until fall, when they are killed by the first frost.

Chinese mantis is distinguished from European mantis by its larger size, the pattern of stripes and shape of plates on the face, a bold green stripe along the edge of the forewing, and a yellow spot between the front legs.

Leafy spurge hawkmoth (Hyles euphorbiae)

leafy spurge hawkmoth
Photo by Lucy Morrissey

Leafy spurge hawkmoth (Hyles euphorbiae) is a large exotic moth. It is native to Europe and western Asia. In the 1960s it was introduced into the United States to control leafy spurge, and separately into Canada to control leafy and cypress spurges. Hawkmoth populations are never large due to predation and disease, and they are susceptible to insecticides used to control grasshoppers. While the larvae can entirely defoliate a host plant, the damage to the host plant population is never significant.

Since its introduction, leafy spurge hawkmoth has spread widely and its range continues to expand. It now occurs in the northern United States and southern Canada east of the Rocky Mountains. It is found from late May through July in disturbed meadows and other grasslands with large populations of leafy spurge. Larvae feed on the foliage of leafy spurge and other members of the Euphorbiaceae (spurge) family. Adults feed on flower nectar. They hover like a hummingbird when visiting flowers.

Leafy spurge hawkmoth is identified by its large size; pale tan forewings with a slight pinkish tinge; a squarish, olive-brown spot in the basal area and another in the median area; an olive-brown post-medial band; and black peppering in the pale areas.

Giant mayfly (Hexagenia limbata)

Giant mayfly
Photo by Luciearl

Giant mayfly (Hexagenia limbata) is a large “common burrower” mayfly. It is very widespread, occurring in the United States and southern Canada from the east coast to the Great Plains and on the west coast. It is mostly absent from the desert and mountain regions in the west. It is the most common mayfly in the Midwest, and is common in Minnesota.

Larvae are found in organic, silty or mucky bottoms of lakes, ponds, and rivers, usually about three meters below the water surface. They feed on organic material suspended in the water. Immature adults are found on trees and bushes on shores near the bodies of water from which they emerged. Adults are found flying in swarms over land near the water body. They do not feed and live from just a few hours to a few days. Emergences are synchronized and can produce swarms so large that they can bee seen by weather satellites. Snow plows are sometimes used to clear dead mayflies off of roads.

Giant mayfly is said to be the largest mayfly in the United States. It can be more than one inch in length, not including two hair-like “tails” that can be equally long. The body may be yellow, yellowish-brown, brown, or even white. Aside from its very large size, giant mayfly is identified by the wing veination, and by the four-segmented end part (tarsus) of the hind leg.

Leonard’s skipper (Hesperia leonardus)

Leonard’s skipper
Photo by Scott Leddy

Leonard’s skipper (Hesperia leonardus) is a large, late season, branded skipper. It occurs in North America east of the Rocky Mountains. It is listed as a Special Concern species in Minnesota, where it is declining due to habitat loss, insecticide drift from nearby croplands, and prescribed burning of managed prairies and savannas.

Adults fly from early August to mid-September. They feed on nectar from many flowers, including wild bergamot, heal-all, round-headed bush clover, asters, goldenrods, spotted knapweed, prairie ironweed, blazing stars, thistles, Joe-pye weed, and sunflowers. Larva feed on grasses.

There are three subspecies of Leonard’s skipper, two of which occur in Minnesota. The western subspecies, Pawnee skipper (Hesperia leonardus pawnee), is found in prairies in the west. The eastern subspecies, Leonard’s skipper (Hesperia leonardus leonardus), is found in dry prairies, savannas, open woodlands, and woodland openings in the east. The ranges of the subspecies overlap in eastern Minnesota, western Iowa, and western Wisconsin. In these areas the subspecies interbreed, producing “blended” offspring that are closer in appearance to Leonard’s skipper. The Leonard’s skippers in eastern Minnesota are all or mostly “blended”.

Northern broken-dash (Wallengrenia egeremet)

Photo by Scott Leddy

Northern broken-dash, Dun skipper, and little glassywing are called “the three witches” because their dark wings make it difficult to tell “which one is which.”

Northern broken-dash (Wallengrenia egeremet) is a small, dark, nondescript, grass skipper. It occurs in the United States and southern Canada east of the Rocky Mountains. It is most common in the northeast from Maine to Michigan south to Massachusetts and Ohio. It is uncommon but sometimes locally abundant throughout its range, including in Minnesota. Adults are found from late June to mid-August in open places near wooded or shrubby areas, including fields, pastures, meadows, woodland edges, gardens, and roadsides. They drink nectar from white, pink, and purple flowers, including alfalfa, red clover, dogbane, New Jersey tea, milkweed, and blazing star. Larva feed on the leaves of panic grasses.

The upper side of both wings is dark brown with pale markings and a brownish fringe. On the male the leading edge of the forewing is pale. The group of specialized scent scales (stigma) on the male forewing is black and is interrupted in the middle, like a “broken dash”. This is the feature that gives the species its common name.