Nemocapnia female, captured by Bill Stark
Plecoptera: Capniidae: Nemocapnia carolina Banks, 1938
Adult stoneflies are relatively flat, soft-bodied, poor-flying insects found near streams and rocky lake shores. Nymphs are normally found under stones in streams and lakes, hence their common name “stoneflies”. Larvae of some species are predaceous, while others are omnivores or plant feeders.
There are about 3,500 known species of Plecoptera in the world with species found on all continents except Antarctica. Of the 650 known species in North America, 24% are in the family Capniidae (1). There are 17 genera of Capniidae in the world and 10 in North America with one species of Nemocapnia: Nemocapnia carolina. In North America, Nemocapnia carolina is distributed throughout Alabama, Arkansas, Florida, Illinois, Indiana, Mississippi, North Carolina, South Carolina, Virginia, and Quebec.
Several species of stoneflies emerge as adults, feed, and mate during the summer months, but since members of the family Capniidae do not emerge until the coldest parts of winter, they are known as “small winter stoneflies” or “snowflies”. The common name of Nemocapnia carolina is the Southern Snowfly. Capniidae adults are usually dark, have long cerci with 4 or more segments, and have small, wedge-shaped mid-tarsal segments. Nemocapnia nymphs have cerci with a dorsal and ventral fringe of long hairs on the apical segments (2).
Nymphs of Nemocarpia carolina dwell beneath rocks, gravel and other debris in lakes and streams. Stoneflies live most of their lives as immatures underwater, and after their final molt they emerge to live only a very short time as adults. The presence of stoneflies is suspected to be an indicator of good water quality and the insects are a significant ecological component to many water systems (2). Delaware even adopted Plecoptera as the state macroinvertebrate in 2005 because it’s an indicator of the excellent water quality in the state!
Nemocarpia carolina mates very soon after emerging as an adult. Males drum on a substrate, such as a branch, with the tip of their abdomen and females respond and answer with a special drumming of their own (3). (See John Sandberg’s page on drumming)
Adults can frequently be seen walking on snow but are often found resting on bridges, rocks, fence posts, and other objects near streams where the nymphs develop. Many can be collected by sweeping the vegetation along banks of streams and a beating sheet is also a great method of collection. Both adults and nymphs should be preserved in alcohol (larvae should first be fixed by boiling) since pinned specimens often shrivel and shrink resulting in diagnostic characters becoming impossible to distinguish. The NCSU Insect Museum has 43 specimens in alcohol from Wake County (collected March, 1958) and Person County (collected January, 1973) North Carolina. In addition, there are 18 species of Allocapnia in the collection.
For more information:
1. Fochetti, R., and J. M. T. de Figueroa. 2008. Global diversity of stoneflies (Plecoptera; Insecta) in freshwater. Hydrobiologia. 595:365–377
2. Pescador M. L., A. K. Rasumussen, and B. A. Richard. 2000. A guide to the stoneflies (Plecoptera) of Florida. Florida Department of Environmental Protection, Division of Water Resource Management, Tallahassee, Florida, U.S.A. 93 pp + data appendix
3. Hynes, H.B.N. 1976. Biology of Plecoptera. Ann. Rev. Entomology. 2 1 : 1 35-53
4. Bill P. Stark, Stanley W. Szczytko, C. Riley Nelson. 1998. American Stoneflies: A photographic guide to the Plecoptera. Columbus, OH. Caddis Press, 126 pp.
7. GBIF records (28 occurrence records in North America, only 1 from NC near Marion in Haywood County, no date)