Northern Blue Butterfly
Lycaeides idas nabokovi Masters

Status: State Endangered (August 1, 1989).

Occurence: Occurs in Florence, Forest, Marinette, and Oconto Counties of Wisconsin.

Aid to ID: This species is nearly indistinguishable from the Karner blue, but is found in a very different habitat. On the upper wings the male is purple-blue, and the female is gray-brown with some blue near the body. The underside of the wings are dull gray speckled with black spots and the hind wing has a band of orange crescents inside blue spots along the entire margin. The adult wingspan is about 1.15-1.45 inches (30-36 mm).

Habitat: The northern blue is found in Wisconsin only in association with the larval host plant, dwarf bilberry (Vaccinium caespitosum), which is also state endangered. Dwarf bilberry occurs in small patches beneath scattered pine on deep, sandy soil in association with bracken, sweet fern, and barrens strawberry in northeastern Wisconsin. The butterflies have been observed nectaring on dogbane, yarrow and clover.

Management Considerations: Little is known about the basic ecology of the northern blue and its association with dwarf bilberry, therefore aggressive management of northern blue sites is not recommended. Succession to forest threatens the viability of habitat patches. Burning to maintain the openings needed for dwarf bilberry appears to be detrimental to the host plant and may also harm unprotected eggs or larvae. Careful cutting, mowing and controlled grazing may be appropriate alternatives. Competition with aggressive species such as sweet fern and bracken in the openings is also problematic for maintaining habitat patches. Timber harvest, planting and piling of logs should be avoided on the few sites supporting northern blue populations. Timber harvest in the general area should be discouraged during the time when puddling males could be crushed on access roads.

The content for this page was originally presented in the Endangered and Threatened Invertebrates of Wisconsin, a free publication available by contacting the Endangered Resources Program.