The butterfly, whose life cycle depends on the wild blue lupine flower (Lupinus perennis), was classified as an endangered species in the United States in 1992.

The Necedah National Wildlife Refuge in central Wisconsin is home to the world's largest population of Karner blues, which benefit from its vast area of savanna and extensive lupine.

The female is grayish brown, especially on the outer portions of the wings, to blue on the topside, with irregular bands of orange crescents inside the narrow black border.

The underside of both sexes is gray with a continuous band of orange crescents along the edges of both wings and with scattered black spots circled with white.

In east-central New York, Karner blue butterflies occurred in 3 rights-of-way habitat types: wild lily-of-the-valley-starflower (Maianthemum canadensis-Trientalis borealis), sweetfern-whorled yellow loosestrife (Comptonia peregrina-Lysimachia quadrifolia), and blackberry-sheep sorrel (Rubus spp.

Increased lupine and nectar abundance, higher temperatures allowing for longer activity periods, and ease of finding mates have been suggested as possible reasons for adult preference of open areas.

[11][12][15] The different brood responses to shade may be due to the direct impact of varying environmental conditions over the course of the season on Karner blue butterflies (see section "Temperature") and the associated effects on wild lupine (see below).

[11][12][14][15] Shade-grown wild lupine being more nutritious, possibly due to nitrogen content limiting photosynthesis to a greater extent in open areas, was one of several explanations.

Parasitoids in the genera Phaeogenes and Orthostigma were all seen in closed habitats, while 90% of damsel bugs (Nabicula subcoleoptrata), a potential predator, were observed in open areas.

In a right-of-way in west-central Wisconsin, the frequency that Karner blue butterflies stayed in an area between recaptures was significantly (p<0.05) positively related to percent cover of nectar flowers such as Canadian horseweed (Conyza canadensis var.

[18] Preliminary results from a study in southeastern Minnesota suggest that openings where Karner blue butterflies were detected tended to have more flowering nectar species.

[11][15][20] For instance, at Fort McCoy in west-central Wisconsin, all the nectar species listed for Karner blue butterflies require either full or partial sun.

[11] The lower temperatures occurring in partial and shaded habitats of Wisconsin and Minnesota meant that 1st-flight females only had access to these areas for a few hours a day.

[16] A review suggests that the cover provided by snowpack protects Karner blue butterfly eggs from hatching prematurely or being overheated by direct sunlight.

Therefore, short periods of continuous snow cover due to site conditions or mild winters could result in decreased occurrence or smaller populations of Karner blue butterflies.

[8][12][15][17] Research at Indiana Dunes National Park led to recommendations for canopy openings for adult males and nectaring of both sexes, as well as areas with 30-60% cover for ovipositing females.

[27] In addition to the effect of amount of wild lupine, a review[7] suggests that it is easier to maintain Karner blue butterfly habitat in larger patches.

Lane[11] notes the need to find a balance between having patches of different required habitats within the activity range of Karner blue butterflies and having open areas large enough that they do not become shaded too quickly.

Maxwell[15] recommends considering the amount of shaded wild lupine habitat within the dispersal distance of Karner blue butterfly when reducing overstory.

The first Karner blue butterfly flight generally occurs sometime between mid-May and mid-June, with males typically appearing earlier than females.

[35][36] Other potential predators of Karner blue butterfly larvae include green lacewings, soldier beetles, and damsel bugs.

Incidental predation of Karner blue butterfly eggs, larvae, and pupae by white-tailed deer grazing on wild lupine can be substantial.

In a study of the effect of different experimental feeding treatments, Karner blue butterfly larvae tended by ants had one of the shortest observed larval durations and gained the most weight for the amount of lupine eaten.

[10] Prior to the heat and drought of 2012 that extirpated several populations in the southern parts of the species range, habitat loss through direct conversion to other land uses and through succession were considered the major causes of the decline of the Karner blue butterfly.

Recovery criteria were addressed,[7][8] while Christenson and Lentz[38] discussed lessons learned while developing a statewide Habitat Conservation Plan for Wisconsin.

In 2023, the National Park Service published a 154-page report, using studies and recommendations that were motivated by population extirpations attributed to the 2012 drought and warmth that were regarded as a harbinger of more such events forthcoming owing to climate change.

[8][22] Effects of mowing, burning, and other management techniques and land uses on the average number of Karner blue butterflies observed per survey hour are included in.

[24] Recommendations on the use of a wide range of management techniques such as thinning, rotational grazing, and planting of wild lupine and/or nectar species can be found in.

[8][15] According to reviews and general field observations, management activities that are typically harmful to Karner blue butterflies include management that increases deer and/or grouse populations, close-cropped grazing, frequent or poorly-timed mowing, plowing, use of herbicides that kill lupine or nectar plants, and use of pesticides that are detrimental to Karner blue butterflies, ants they associate with, or pollinators of species they use for nectar.

Creation and rotation of management units should incorporate this information as well as data on Karner blue butterfly movement (see section "Timing of major life history events").