Minnesota Butterflies

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, common self-heal, 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, 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.

Iowa skipper (Atrytone arogos iowa) is a species of special concern in Minnesota. Its populations are restricted to undisturbed tallgrass and shortgrass prairies in the Great Plains. Massive habitat destruction and excessively frequent prescribed burning on managed prairies are major threats to the subspecies survival. It is declining in the northern parts of its range. It is no longer found in 200 western counties it was once known from. It is estimated that there are over 100 remaining populations, but those are small and scattered. It is considered uncommon to rare wherever it occurs. In Minnesota, it is found mostly in the southwest quarter of the state.

Iowa skipper is a small to medium-sized grass skipper. The wings are yellowish-orange with a broad, dark border. The female has a thin black streak in the center of the forewing, but otherwise the wings are unmarked. When at rest, the forewings are held at a 45° angle and the hindwiings are held horizontal, a configuration that resembles an F-15 Eagle fighter jet.

Iowa skipper is similar in appearance to the Delaware skipper (Anatrytone logan), which is much more common. Iowa skipper is distinguished by the lack of any black veining on the upperside of the wings; lack of a black cell end bar on the forewing; wing undersides not as bright; and the hindwing fringe that is usually white, not tan or orange.

Wild indigo duskywing (Erynnis baptisiae) is a medium-sized spread-wing skipper. It is widespread, abundant, and increasing in the east and the Midwest, but rare in Minnesota.

Wild indigo duskywing was originally a species of open woodlands and shrubby prairies. The larvae fed on mostly on horseflyweed but also blue wild indigo and sundial lupine. With the decline of those species due to habitat loss, the skipper adapted to the introduced, locally abundant species crown vetch. Today, its range is rapidly expanding and its numbers are increasing wherever crown vetch has been widely planted.

Wild indigo duskywing has dark brown wings; a pale spot at the end of the forewing cell; and four translucent white spots at the leading edge near the tip of the forewing. Along with columbine duskywing and Perseus duskywing, it is part of the “Persius species complex”. They are very similar in appearance and difficult or impossible to distinguish in the field. Columbine duskywing is smaller, lighter, and has shorter wings. Perseus duskywing has not been recorded in Minnesota.

Checkered white (Pontia protodice) is a medium-sized butterfly with a wingspan of 1½″ to 2½″. It is a southerly species and is uncommon in Minnesota. There are two overlapping broods here, early June to August (spring form) and July to mid-October (summer form). The wings are white with dark markings, including a checkered pattern on the outer margin. The female has more extensive markings than the male, and the spring form has darker markings than the summer form. The larva (caterpillar), known as the southern cabbageworm.

Checkered white populations have drastically decreased in eastern Unites States, and the butterfly is now scarce or extirpated in some areas where it was once common. It appears stable in the west. The cause of the decline is unknown, though habitat loss is certainly a contributor. It is possible that the extremely abundant introduced species cabbage white is displacing native whites, including checkered white. It is also possible that checkered white is a western and midwestern species that only sporadically became abundant in eastern agricultural fields. It remains to be seen whether the decline will continue to spread westward.

fiery skipper (Hylephila phyleus)

sachem (Atalopedes campestris)

American snout (Libytheana carinenta)

Acadian hairstreak (Satyrium acadica)

brush-footed butterflies (family Nymphalidae)

Compton tortoiseshell (Nymphalis l-album)

common checkered-skipper (Burnsius communis)

Monarch (Danaus plexippus) migration is well documented and much studied. In September, adults of the third or fourth generation of the eastern population of monarchs begin congregating in large numbers on the foliage of trees and shrubs near water. By the end of October they have left the state in a mass migration to their winter grounds. They arrive at one of thirteen small overwintering sites in the Sierra Madre mountains between 43 and 105 miles west of Mexico City, Mexico. The following spring the same butterflies begin a northward migration. They lay eggs that will become the first generation in northern Mexico and southern United States between late March and late April. First generation monarchs begin to arrive in Minnesota around mid-May. Northward migrating butterflies arrive in Minnesota around mid-May. They are of a more recent (first) generation, rarely if ever the same individuals (third or fourth generation) that migrated south.

Less is known about migration of other butterfly species in North America. There is some disagreement about whether any of them, other than the monarch, migrate south in the fall. There are numerous reports of southward movement or “migration” of butterflies in the literature. However, the reports that I have seen in researching this article, both in print and online, are observational in nature. They do not involve a scientific study of any kind, and may be explained in terms that do not involve migration in its strict sense.

Many species cannot survive our harsh winters and die with the arrival of cold temperatures. Their populations are restored the following spring and summer as the seasonal range once again expands into Minnesota. Sometimes an outbreak in the south is followed by large numbers of butterflies being swept north on weather fronts. Both of these northward seasonal movements, while occurring in large numbers, lack intentionality. They could be called “seasonal immigration” to distinguish them from the true migration of the monarch.

Red admiral (Vanessa atalanta) migration is well documented in Europe but less not on this side of the Atlantic. The Red Admiral and Painted Lady Research Site states that some red admirals in parts of their North American range move south in the fall and some stay behind. It is not known how many non-migratory individuals in the northern parts of their range successfully overwinter. The “migration” is thought to be one way, meaning that the individuals that move south in the fall are not the same individuals that move north in the spring. The distance of the southward movement is not known, whether it is all of the way or only part of the way to the southern limits of their range.

Numerous sources report that painted lady (Vanessa cardui) butterflies migrate south, and that the migration begins in August and continues through November. Painted lady butterflies overwinter in the southwestern United States and in northern Mexico. They immigrate north in the spring in most years, temporarily repopulating the United States and Canada. Some years they do not immigrate at all. In years of much rain on the wintering grounds the northward immigrations are enormous. The El Niño of 2015 is expected to last into the spring of 2016 and should bring much rain to the wintering grounds of the painted lady.

American lady (Vanessa virginiensis) butterflies are the hardiest species of Vanessa butterflies. The field guide Butterflies through Binoculars: The East (1999) states that the American lady “Migrates south in the fall...”. In the northern part of its range some may overwinter as adults, hidden in a crevice of tree bark or a human dwelling. In the spring American lady butterflies immigrate north, repopulating northern United States and Canada.

Some anglewing species are reported to have both migrating and non-migrating individuals, and that migrating adults move south in the fall. Overwintering adults wedge themselves into small crevices in trees or human buildings. They sometimes fly about on warm sunny days in the dead of winter.

Question marks (Polygonia interrogationis) are said to have both migrating and non-migrating individuals. Mourning cloaks (Nymphalis antiopa) are reported to have some migrating individuals by, among other sources, the popular Website Butterflies and Moths of North America, and the field guide Butterflies through Binoculars: The East (1999). According to an entomologist with the Minnesota DNR, “these are movements in response to crowding resulting from a local outbreak.”

Compton tortoiseshell (Nymphalis vaualbum) and Milbert’s tortoiseshell (Aglais milberti) butterflies hibernate, sometimes in groups. Variegated fritillary (Euptoieta claudia) does not survive Minnesota winters. It immigrates into Minnesota each year.

Monarch