Northern Blue (Lycaeides idas), listed as Endangered in Wisconsin, is found in pine barrens, and 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 fern (Pteridium aquilinum), sweet fern (Comptonia peregrine), and barren strawberry (Waldsteinia fragarioides) in northeastern Wisconsin. The flight period extends from late-June to mid-July.