Observations on <i>Lycaeides</i> in the Northern Midwest, USA (Lepidoptera: Lycaenidae).

Abstract

On transect butterfly surveys during 1990-99, we recorded northern blues (Lycaeides idas nabokovi) in forest openings in northeastern Wisconsin, Kamer blues (L. melissa samuelis) in barrens in central and northwestern Wisconsin, and melissa blues (L. m. melissa) in prairies in western Minnesota and adjoining North and South Dakota. Each taxon was surveyed within that part of its range where only that taxon is known to occur. We compared identification features described in field guides to our photographs of multiple individuals of all three taxa. These features were subtle and overlapping among taxa in midwestern individuals. Accurate field identification is applicable to populations but not isolated individuals, and must be based on a number of individuals, in conjunction with range and habitat characteristics. All three taxa tolerated some habitat degradation, based on their nectar visits to exotic plants and the vegetative characteristics of occupied sites. But northern and Karner blues were localized in distribution, where they might reach relatively high densities (individuals observed per hour), while the melissa blue occurred in more vegetation types but generally lower densities. Density (i.e., detectability) of Karner and melissa blues (the two analyzable taxa) increased with rising temperature and during later hours in the survey day and decreased with increasing wind speed. Males of sexed individuals averaged 70% for Karner blue and 78% for melissa blue. Although Karner and melissa blues in this study occurred in similar latitudinal ranges, they did not show consistent seasonal correspondence in their flight period curves. The single observation date of northern blues, which had a relatively high density, fell between two low-density Karner blue dates (one in the spring generation, the other in the summer), and consisted of 83% males.