Overview
The Karner blue butterfly, an endangered species, is a small butterfly that lives in oak savannas and pine barren ecosystems from western Wisconsin and eastward to the Atlantic seaboard. Historically, it was found in a continuous band throughout its range, but today is found in portions of New Hampshire, New York, Michigan, Wisconsin and Ohio. Wild blue lupine (Lupinus perennis) is the only plant Karner blue larvae, or caterpillars, can eat. Even so, the range of these butterflies and that of their host plant do not completely overlap. Instead, Karner blue butterfly are found predominantly along the northern band of wild lupine's range.
At the time of listing under the Endangered Species Act, the most important factor causing the decline of the Karner blue butterfly across its range was the loss of habitat due to suppression of wild fires, clearing land for farming and developing land for commercial and residential purposes. Without disturbance activities like fire and grazing, shrubs and trees invade the open savanna and barrens, shading out grass and herbaceous plants like wild lupine. When this happens, only pockets of suitable space remain, which make it hard for butterflies to find more areas with wild lupine. It also limits the amount of suitable habitat that's available. This results in small, isolated populations of Karner blue butterflies. Because the Karner blue butterfly's habitat is very specific, the butterfly is unable to adapt to these changes in its environment. Habitat loss and isolation of these populations, combined with the extremely small size of many of the remaining population, puts many populations at high risk of winking out of existence.
The Karner blue butterfly has also been found to be highly sensitive to both direct and indirect climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change impacts as was documented in 2019 during the U.S. Fish and Wildlife Service 5-year review. The likely extirpation of the population at the Indiana Dunes National Lakeshore was used as a case study to explore the Karner’s sensitivity and exposure to climate change. Findings indicate that the population’s decline occurred in conjunction with documented warming conditions. Additionally, the documented decline is considered consistent with scientists’ expectations for how a population of a low-motility species at the edge of the climate-induced range would respond.
Efforts to conserve and recover this butterfly continue to occur throughout the Karner blue range. The U.S. Fish and Wildlife Service prepared the Karner Blue Butterfly Recovery Plan in 2003, which outlines a strategy for recovering the butterfly range-wide. It identifies tasks to restore habitat, as well as ways to stabilize and recover Karner blue populations. A wide variety of partners are committed to protection and restoration of the Karner blue butterfly and its habitat on public and private lands throughout the range. Also, there is a large recovery group that is committed to researching less understood aspects of Karner biology and habitat management.
Scientific Name
Identification Numbers
Characteristics
Life Cycle
The Karner blue butterfly usually has two generations, and thus two flight periods, each year. Timing for each life stage varies slightly by location within the range. Typically sometime in April the first group of caterpillars hatch from eggs that were laid the previous year. The caterpillars then feed only on wild lupine plant leaves. By about mid-May, the caterpillars pupate and adult butterflies emerge from their cocoon-like chrysalis by the end of May or in early June. These adults mate, laying their eggs in June on or near wild lupine plants. The eggs hatch in about one week and the caterpillars feed for about three weeks. They then pupate and the summer's second generation of adult butterflies appears in July. These adults then mate and lay eggs that will not hatch until the following spring.
The Karner blue butterfly usually has two generations, and thus two flight periods, each year. Timing for each life stage varies slightly by location within the range. Typically sometime in April the first group of caterpillars hatch from eggs that were laid the previous year. The caterpillars then feed only on wild lupine plant leaves. By about mid-May, the caterpillars pupate and adult butterflies emerge from their cocoon-like chrysalis by the end of May or in early June. These adults mate, laying their eggs in June on or near wild lupine plants. The eggs hatch in about one week and the caterpillars feed for about three weeks. They then pupate and the summer's second generation of adult butterflies appears in July. These adults then mate and lay eggs that will not hatch until the following spring.
The Karner blue butterfly usually has two generations, and thus two flight periods, or the time that adult butterflies are on the wing, each year. Timing for each life stage varies slightly by location within the range. Typically sometime in April the first group of caterpillars hatch from eggs that were laid the previous year. The caterpillars then feed only on wild lupine plant leaves. By about mid-May, the caterpillars pupate and adult butterflies emerge from their cocoon-like chrysalis by the end of May or in early June. These adults mate, laying their eggs in June on or near wild lupine plants. The eggs hatch in about one week and the caterpillars feed for about three weeks. They then pupate and the summer's second generation of adult butterflies appears in July. These adults then mate and lay eggs that will not hatch until the following spring.
Physical Characteristics
The male and female of this small butterfly are different in appearance. The topside of the male is silvery or dark blue with narrow black margins. 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.
The Karner blue butterfly is a small butterfly with a wingspan of about one inch, often compared to the size of a postage stamp.
Food
Karner blue caterpillars feed only on the leaves of the wild lupine (Lupis perennis) plant. Adults feed on the nectar of flowering plants. Because the caterpillar can only successfully feed on wild lupine, the reproductive success of Karner blue butterflies is critically dependent on the wild lupine.
Similar Species
The Karner blue butterfly is a subspecies of the Melissa blue butterfly. The Melissa blue typically has three broods, whereas the Karner only has two.The Karner caterpillars feed only on wild lupine and the Melissa blue may feed on various legumes of the pea family including Astragalus, Glycyrrhiza, Lotus, Lupinus and Medicago species.
Habitat
Adult karners can fly up to about 1.4 miles across open landscapes. Adults will mate and then lay eggs on wild lupine plants. Karner caterpillars feed on wild lupine leaves and are commonly tended by ants. It appears the ants protect the caterpillars from some natural enemies and that the ants in return collect a nectar from the caterpillar. Once mature, the caterpillars pupate.
Ecosystem with large, flat areas of grasses.
Behavior
Adult karners can fly up to about 1.4 miles across open landscapes. Adults will mate and then lay eggs on wild lupine plants. Karner caterpillars feed on wild lupine leaves and are commonly tended by ants. It appears the ants protect the caterpillars from some natural enemies and that the ants, in return, collect a nectar from the caterpillar. Once mature, the caterpillars pupate.
Geography
Karner blue butterflies once occurred in a nearly continuous narrow band across 12 states and the province of Ontario, Canada, but it has been eliminated from seven of those states and Ontario. Today it is found in portions of New Hampshire, New York, Michigan, Wisconsin and Ohio.
Timeline
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