Butterfly species in Lewis and Clark County, Montana and comparison to those of Missoula County, Montana and Alberta, Canada

The butterflies of Lewis and Clark County were studied and then compared to Missoula County and the Province of Alberta. Missoula County is on the west side of the Continental Divide, while Alberta and Lewis and Clark County are east of the Divide. Believing that the Divide may limit east-west migration, I hypothesized that the fauna of Lewis and Clark County would more closely resemble the fauna of Alberta than that of Missoula County. For Lewis and Clark County, butterflies were captured, killed, mounted, and identified from eight sites. Collection took place from May 25 to July 27, 2001. My collection data of 69 species was combined with previous collection data from Dr. Steve Kohler (personal communication) and Dr. John Christenson (personal communication) for analyzing results. The combined data was used to create distribution maps and flight period tables for Lewis and Clark County. Lists were compiled for each ofthe three regions and then compared. While distribution maps reveal where certain species can be found, flight period tables represent the known times of emergence for different butterfly species. The comparison of compiled lists from Lewis and Clark County and Missoula County and Alberta showed Lewis and Clark County to more closely resemble Missoula County. These analyses allow for a more thorough understanding of the species found within Lewis and Clark County and for the comparison of Lewis and Clark County’s species to the other two regions.