Endangered Species
Mountain-Prairie Region
Western Glacier Stonefly

Zapada columbiana

The western glacier stonefly (Zapada glacier) is a species of insect in the taxonomic order Plecoptera, also known as the stonefly order.  Adults are dark-colored and have a body length and wing length ranging from 0.2 to 0.4 inches.  The females are almost twice the size of males.  The immature stage (nymph) of the western glacier stonefly has not been described.

The western glacier stonefly has only been found in or near five streams on the east side of the Continental Divide in Glacier National Park in northern Montana.  All but one of the western glacier stonefly specimens were collected between 1963 and 1969. 

We do not know how many western glacier stoneflies exist or if the species is still extant.  No specimens have been reported since 1979.  In the past the species appears to have been quite rare.  Only 25 specimens have been collected in total with only 1 to 4 individuals collected at any one survey location. 

There is little information available regarding the life history of the western glacier stonefly.  In general, stoneflies are typically found in clean, cold running waters that have high oxygen content.  Therefore, they are sensitive to temperature and chemical changes in their environments.  Their presence can be an indication of a healthy stream ecosystem. 

Recent Actions:
The Service completed a 90-day finding on a petition to list the western glacier stonefly under the Endangered Species Act (ESA).  After evaluating all of the scientific information described or cited in the petition and information readily available in our files, we concluded that the petitioners provided substantial information indicating that protecting the species under the ESA may be warranted.  Therefore, we are initiating a full biological status review to determine if listing the species is warranted.

Last updated: December 19, 2011