Butterflies are blossoming in Michigan as spring makes way for summer. Among them is a small, native butterfly with a big, blue color.
The Karner blue butterfly is an attractive little creature with a wingspan of about one inch. It is roughly the size of a postage stamp.
Males have a vibrant blue color on their upper wings and a single row of metallic blue-green, orange and black spotted rims on the outer edges of their wings’ underside.
The upper surfaces of the female’s wings are blue close to its body and fade to a gray-brown at the edges. The Karner blue feeds on the nectar of a variety of flowers such as lupine, New Jersey tea, dogbane and butterfly weed. Larvae of the Karner blue feed only on wild lupine leaves and flowers.
Due to the larvae’s specific diet, the female Karner Blue only lays her eggs on or near lupine plants. After hatching, the young caterpillars feed on the lupine and form a chrysalis after a few weeks of feeding. Adults emerge in about ten days. Two generations are produced each summer.
Michigan lupine can be found in various oak savannas, oak-pine barrens and other open areas containing sandy soil, according to the Michigan Natural Features Inventory. But many of the habitats conducive to lupine survival are in decline.
Once ranging from Maine to Minnesota, the Karner blue butterfly has been reduced to small populations in Indiana, Michigan, Minnesota, New Hampshire, New York and Wisconsin, according to a U.S. Fish and Wildlife Service report.
In Michigan, the historical distribution of Karner blue butterfly was widespread in the western and southern Lower Peninsula, but populations declined as the amount of habitat available for lupine was reduced. This reduction was the result of development, agriculture and fire suppression.
The inventory said before the arrival of European settlers, fire was essential in maintaining prairies, savannas and barrens. Periodic fire killed trees and shrubs, allowing other ground forbs like wild lupine, butterfly weed and coreopsis to grow. Today, these fires are very rare and other trees and shrubs have invaded the butterfly’s natural habitat, shading out many ground plants.
The Karner blue butterfly is listed as a federally endangered species and as threatened in the State of Michigan. Today, it persists in remnants of savanna and barrens, degraded openings, old fields, and utility and highway rights-of-way.
Reintroducing fire through prescribed burns will help maintain remaining savanna areas. Federal, state, and private landowners are partnering in various habitat management practices to maintain Karner blue habitat. The Toledo Zoo is also studying techniques to breed the Karner blue in captivity for later release into the wild.
−Originally published in MNA’s July 2007 newsletter−