Rare Species Guide

  Synonyms

Lycaeides melissa samuelis, Plebejus samuelis, Lycaeides samuelis, Plebejus melissa samuelis

  Basis for Listing

The historical range of the Karner Blue (Plebejus samuelis) lies in a narrow band from Maine and New Jersey westward through the southern Great Lakes region to eastern Minnesota and northeastern Iowa (Dirig 1994). It was always a highly local species because of the naturally patchy distribution of its specialized habitat, sandy barrens and savannas where its obligate larval host plant, wild lupine (Lupinus perennis), occurs. Human land use has had a severe impact on this habitat, resulting in the disappearance of many colonies and the reduction of most others to precariously small numbers of adult butterflies. The Karner Blue is believed to be extirpated in several states (and the Province of Ontario) and is barely hanging on in several others (NatureServe 2025). Only in Wisconsin are there still numerous colonies, including several sizeable metapopulations (Bleser 1994).

Appropriate habitat for the Karner Blue was rare in Minnesota even before colonial settlement. Wild lupine reaches the western limit of its range in central Minnesota, and within this range its occurrences were always very discontinuous, reflecting the distribution of extensive sand deposits. Commercial and residential development and succession of savanna to closed woodland and forest following fire suppression have eliminated many wild lupine populations or reduced them to small numbers of plants in scattered openings. The Karner Blue was not discovered in Minnesota until 1975, making its pre settlement status here speculative. It has been confirmed at only two locations in the state: one in the Anoka Sand Plain north of the Twin Cities and one in The Blufflands in Winona County. The former site supported a very small colony at the time of its discovery in 1975, and this died out in the 1980s. The latter site comprises a number of habitat patches distributed over a fairly large area. From its discovery here in 1978 through 1983, butterfly numbers were reported to be “fairly strong” in the one habitat patch visited during this period (R. Huber, cited in Lane and Dana 1994). But subsequent surveys beginning in 1990, although finding butterflies in additional patches within the site, consistently reported small numbers (Lane and Dana 1994). Searches in 1990 of many sites in the Anoka Sand Plain and the Blufflands that were identified as potential habitat failed to find any new occurrences (Cuthrell 1990). The last detected occurrences of Karner Blue in Minnesota were in 2005 and subsequent surveys have resulted in non-detections. It is presently thought to be likely extirpated from Minnesota. The Karner Blue was originally listed as a threatened species in Minnesota in 1984, but because of its extreme rarity in the state it was reclassified as endangered in 1996. It has been federally listed as endangered by the U.S. Fish and Wildlife Service since 1992.

  Description

The Karner Blue is a member of the family Lycaenidae, typically small colorful butterflies sometimes known as gossamer-wings. It belongs to a distinctive group of species within the family commonly known as “blues” because of the blue coloration of the upper wing surfaces in males of many of the species (females are usually more brown than blue). It is a small butterfly, forewing length 1.2-1.5 cm (0.5-0.6 in.) from base to apex, with rounded wings. Males and females are nearly identical in size and shape. The upper surfaces of both hind and forewings of males are bright violet- or lilac-tinged blue with a slight frosting of whiter scales in fresh individuals, especially along the veins. There is a thin black line along the outer edge of the wings and a contrasting fringe of long white scales. The thorax above is clothed in a dense pile of blue hairs. The female is mostly dark brown above, with blue scaling confined to the basal area of the wings. There is a row of circular black spots near the outer margin of the hindwing that are capped on their inner sides with orange crescents. Beneath, the sexes are nearly identical with a sparse pattern of white-ringed black spots on a pale gray ground (sometimes darker gray in females). Near the outer margin of the hindwing there is a band of prominent bright reddish-orange crescents, each enfolding a silvery-blue eye and thinly capped on the inner edge with black. Smaller orange spots without the silvery inclusions continue the band along the forewing.

There are several other blues in Minnesota that might be mistaken for the Karner Blue. Most similar is the Melissa Blue (Plebejus melissa melissa). Males are virtually indistinguishable, but the orange crescents on the upper side of the hindwing of female Melissa Blues are enlarged and nearly fused into a continuous band, and this orange band continues along the outer edge of the forewing. The basal blue scaling is also greatly reduced compared with the Karner Blue or, more typically, absent. The two subspecies are indistinguishable on the basis of the underside of the wings. The Melissa Blue occurs widely in the prairie part of Minnesota, west of the range of the Karner Blue, but several colonies have recently been discovered within the Karner's range. Nabokov's Blue (Plebejus idas nabokovi) is also quite similar. Again, males are extremely difficult to separate. Typically the orange markings on the lower surfaces of the wings are smaller in Nabokov's than in the Karner, but genitalic dissection is needed for confident determination. Females have, at most, only traces of orange on the upper hindwing. Nabokov's Blue occurs in the forested northern part of Minnesota. The Eastern Tailed-Blue (Cupido comyntas) is smaller than the Karner Blue and has a tiny threadlike tail on each hindwing. The orange spots on the hindwing are small, and only two are usually present. Other blues that are likely to be encountered within the Minnesota range of the Karner Blue lack any orange markings at all. These include the Silvery Blue (Glaucopsyche lygdamus) and the azures (Celastrina lucia and C. neglecta).

  Habitat

Patches of oak savanna on sandy fill in coulee bottoms where wild lupine is common are the habitat of the blufflands colonies of the Karner Blue butterfly. The Sand Plain colony was concentrated along an unimproved township road through an overgrown savanna on sand. Although wild lupine plants could still be found in the overgrown savanna away from the road, the butterfly utilized primarily a small population of vigorous plants along the road edges (Lane and Dana 1994). Similar sandy savanna habitats are reported for the butterfly in Wisconsin and Michigan (Swengel and Swengel 1997; Nielsen 1999).

  Biology / Life History

The Karner Blue has two generations each year throughout its range, including Minnesota. Eggs laid by the second generation females overwinter and hatch early in the spring. These eggs are laid on various plant materials near the bases of wild lupine plants, and in spring the tiny hatchling larvae have to find their way to lupine shoots emerging from the soil. The first generation adults can begin to appear in mid-May and are mostly gone by late June. Year-to-year variation in the rate of warm-up can advance or retard the flight period. Females of the first generation lay their eggs on lupine stems and leaves. Second generation adults emerge and fly beginning as early as mid-July and continuing into late August. Adult life expectancy in the wild is estimated to be only a few days.

Wild lupine is the only known larval host plant throughout the range of the Karner Blue. Larvae feed on leaves and to some extent also on developing fruits (personal observation). Larvae are attended by ants, especially large Formica species that react aggressively to potential predators approaching the larvae (Savignano 1994; personal observation). Like many lycaenid butterflies, Karner Blue larvae have a specialized organ that secretes a sweet liquid avidly fed on by ants and other organs that produce chemicals that mimic ant pheromones to further manipulate ant behavior (Malicky 1970). This ant association helps protect larvae from predatory or parasitizing insects (Savignano 1994). Larvae rest on the wild lupine plants when not feeding and pupate primarily in leaf litter (Lane 1999). Adults of both sexes visit flowers for nectar, and males also imbibe from animal dung and moist sand.

Males seek receptive females primarily by flying about lupine patches searching for them, though they will also pursue as potential mates other insects that fly nearby while they are resting or basking. Other Karner Blue males are the most frequent object of such chases. Dispersal behavior is poorly understood. Most observers have reported that adults tend to remain within small areas, but a few studies have suggested that longer-distance dispersal events (1.5-2 km; 0.9-1.2 mi.) may not be rare (U.S. Fish and Wildlife Service 2003). What conditions are barriers to movement among habitat patches, and conversely, what conditions are conducive to movement, are mostly a matter of speculation.

  Conservation / Management

The small size of the only known Minnesota colony is the primary threat facing the Karner Blue in the state. Such a small isolated colony is at high risk of extirpation resulting from both natural events (such as severe drought or hailstorms) and human caused ones (such as insecticide application) as well as from the vagaries of normal population processes (for example, by chance all adults in one generation are males). Loss of genetic diversity in a small population is another possible threat. The Minnesota colony is at least 80 km (50 mi.) from the nearest known occurrences in Wisconsin (Eau Claire and Jackson counties), making it unlikely that immigration from the Wisconsin population will maintain genetic diversity.

The possible fragmentation of this small colony into even smaller units confined to the separate patches of suitable habitat aggravates the risk of extirpation. Fire suppression has allowed the original oak scrub and woodland matrix to grow up into dense woodland and forest that probably impedes butterfly movement among the patches, and even the patches themselves have been shrinking as oaks invade. The Karner Blue is probably highly susceptible to fire, as eggs or small larvae, which would be the exposed stages during the times most management burning is done, exhibit no obvious adaptations that would shield them from lethal temperatures (Swengel 1994). However, wild lupine responds to dormant season fire with vigorous growth, and the butterfly quickly recolonizes burned areas if there are adults available (Swengel 1994). Therefore, burn units and rotations should be designed to insure that adults will be available to recolonize and that enough time elapses between burns for numbers to rebound. Mechanical clearing is an option where fire would be risky, but the long term suitability of areas managed exclusively with mechanical clearing is unknown. Opening up woodland and forest between patches to provide greater connectivity can be done at little or no risk to the butterflies.

The oak-dominated woodlands and forests here are prime candidates for defoliating outbreaks of the Spongy Moth (Lymantria dispar).  Recent efforts to manage spongy moth with  the toxin derived from the bacterium Bacillus thuringiensis var. kurstaki (Btk), are likely to have considerable impacts to Karner Blue if they are still present  (Herms et al. 1997). It will be imperative to keep application this product well away from Karner Blue habitat.

Recently discovered colonies of the Melissa Blue in eastern Minnesota and western Wisconsin that are using introduced legumes, such as alfalfa (Medicago sativa) and crown vetch (Securigera varia) as larval hosts, pose a new threat. Both legumes are widely planted within the Karner Blue's range, creating the opportunity for the Melissa Blue to invade and hybridize with the Karner Blue. This could lead to the eventual disappearance of the Karner Blue through genetic swamping. Recent molecular studies have found that genetic differentiation between these two taxa is very weak (Packer et al. 1998; Nice et al. 2000), suggesting that hybridization will be likely and that offspring of hybrids and backcrosses will be viable.

  Conservation Efforts in Minnesota

In September 2003, the U.S. Fish and Wildlife Service completed a national Karner Blue Butterfly Recovery Plan. The objective of the plan is to restore viable metapopulations of Karner Blues across the species extant range so that it can be reclassified from endangered to threatened and eventually removed from the federal endangered species list altogether.

All of the known habitat occupied by the Karner Blue in Minnesota is within a state Wildlife Management Area, and DNR mounted a research and management effort on behalf of the butterfly at this site (see video). Fire and mechanical clearing have been used to improve existing habitat and to open up overgrown potential habitat. This effort included annual monitoring of adult abundance. There has been no confirmed sighting of the Karner Blue in the blufflands site since 2005, and regular monitoring there has been discontinued.

  Authors/Revisions

Robert P. Dana, Ph.D. (MNDNR), 2025
(Note: all content ©MNDNR)

  References and Additional Information

Bleser, C. A. 1994. Karner Blue Butterfly survey, management and monitoring activities in Wisconsin: 1990-Spring 1992. Pages 153-162 in D. A. Andow, R. J. Baker, and C. P. Lane, editors. Karner Blue Butterfly: a symbol of a vanishing landscape. Miscellaneous Publication 84-1994, Minnesota Agricultural Experiment Station, University of Minnesota, St. Paul, Minnesota.

Cuthrell, D. L. 1990. Status of the Karner Blue Butterfly, Lycaeides melissa samuelis Nabokov, in Minnesota 1990. Report submitted to the Nongame Wildlife Program, Minnesota Department of Natural Resources. 44 pp. + appendix.

Dirig, R. 1994. Historical notes on Wild Lupine and the Karner Blue Butterfly at the Albany Pine Bush, New York. Pages 23-36 in D. A. Andow, R. J. Baker, and C. P. Lane, editors. Karner Blue Butterfly: a symbol of a vanishing landscape. Miscellaneous Publication 84-1994, Minnesota Agricultural Experiment Station, University of Minnesota, St. Paul, Minnesota.

Herms, C. P., D. G. McCullough, L. S. Bauer, R. A. Haack, D. L. Miller, and N. R. Dubois. 1997. Susceptibility of the endangered Karner Blue Butterfly (Lepidoptera: Lycaenidae) to Bacillus thuringiensis var. kurstaki used for gypsy moth suppression in Michigan. The Great Lakes Entomologist 30:125-141.

Lane, C., and R. Dana. 1994. The status of the Karner Blue Butterfly in Minnesota. Pages 113-122 in D. A. Andow, R. J. Baker, and C. P. Lane, editors. Karner Blue Butterfly: a symbol of a vanishing landscape. Miscellaneous Publication 84-1994, Minnesota Agricultural Experiment Station, University of Minnesota, St. Paul, Minnesota.

Lane, C. P. 1999. Benefits of heterogeneous habitat: oviposition preference and immature performance of Lycaeides melissa samuelis Nabokov (Lepidoptera: Lycaenidae). Dissertation, University of Minnesota, St. Paul, Minnesota. 185 pp.

Malicky, H. 1970. New aspects on the association between lycaenid larvae (Lycaenidae) and ants (Formicidae, Hymenoptera). Journal of the Lepidopterists' Society 24:190-202.

NatureServe. 2008. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.0. NatureServe, Arlington, Virginia. . Accessed 3 June 2008.

Nice, C. C., G. Gelembiuk, N. Anthony, and R. French-Constant. 2000. Population genetics and phylogeography of the butterfly genus Lycaeides. April 21, 2000 report to U.S. Fish and Wildlife Service, Fort Snelling, Minnesota. 43 pp.

Nielsen, M. C. 1999. Michigan butterflies and skippers: a field guide and reference. Michigan State University Extension, East Lansing, Michigan. 248 pp.

Packer, L., J. S. Taylor, D. A. Savignano, C. A. Bleser, C. P. Lane, and L. A. Sommers. 1998. Population biology of an endangered butterfly, Lycaeides melissa samuelis (Lepidoptera: Lycaenidae): genetic variation, gene flow, and taxonomic status. Canadian Journal of Zoology 76:320-329.

Savignano, D. A. 1994. Benefits to Karner Blue Butterfly larvae from association with ants. Pages 37-46 in D. A. Andow, R. J. Baker, and C. P. Lane, editors. Karner Blue Butterfly: a symbol of a vanishing landscape. Miscellaneous Publication 84-1994, Minnesota Agricultural Experiment Station, University of Minnesota, St. Paul, Minnesota.

Swengel, A. B. 1994. Observations on the effects of fire on Karner Blue Butterflies. Pages 37-46 in D. A. Andow, R. J. Baker, and C. P. Lane, editors. Karner Blue Butterfly: a symbol of a vanishing landscape. Miscellaneous Publication 84-1994, Minnesota Agricultural Experiment Station, University of Minnesota, St. Paul, Minnesota.

Swengel, A. B., and S. R. Swengel. 1997. Co-occurrence of prairie and barrens butterflies: applications to ecosystem conservation. Journal of Insect Conservation 1:131-144.

U.S. Fish and Wildlife Service. 2003. Final Recovery Plan for the Karner Blue Butterfly (Lycaeides melissa samuelis). U.S. Fish and Wildlife Service, Fort Snelling, Minnesota. 273 pp.