Illinois Stonefly

Allocapnia illinoensis Frison, 1935

Allocapina illinoensis
C. Riley Nelson 1996

Insecta (Insects)
State Protection
Not Listed
Not listed or protected by New York State.
Federal Protection
Not Listed
State Conservation Status Rank
Not Ranked - State conservation status not yet assessed.
Global Conservation Status Rank
Vulnerable globally - At moderate risk of extinction due to rarity or other factors; typically 80 or fewer populations or locations in the world, few individuals, restricted range, few remaining acres (or miles of stream), and/or recent and widespread declines.


Did you know?

Illinois Stoneflies remain active in the winter because they produce a special protein that keep them from freezing in the cold.

Conservation and Management

Conservation Strategies and Management Practices

Avoiding damming and flow alteration will help maintain favorable habitat for the Illinois Stonefly. Streams should be buffered to reduce agricultural and pesticide pollution. Reduction of road salt usage in transportation corridors near streams will benefit the conservation of this species (NYSDEC 2005).



Stoneflies require clean, fast flowing streams and rivers. Adults may be found climbing the trees during the winter and early spring months in the proximety of cold water streams.


New York State Distribution

The distribution of this species is unknown in New York State. There is one historical occurrence of this species in New York in the Susquehanna watershed (Otsego County) and one recently recorded occurrence in the Lake Champlain watershed (Clinton County) (Myers et al. 2010).

Best Places to See

  • (Clinton, Otsego Counties)

Identification Comments

Identifying Characteristics

Illinois stonefly larvae have two long filamentous cerci and have an elongated or flattened appearance. They also have long antennae, chewing mouthparts, gills on the abdominal segments, and pairs of thoracic wing pads. Adults are similar to the larvae except they have two pairs of wings folded over the abdomen and the gills are absent of vestigial (Hilsenhoff 1995).

Males of the Allocapina genus have varied and raised lobes on the dorsal abdominal segments (Frison 1929). Females are more difficult to distinguish.

Best Life Stage for Proper Identification



Illinois Stoneflies feed on the leaf litter and detritus that falls into the streams, especially in the fall.

Best Time to See

The Illinois Stonefly lives most of its life within the stream, around one to two years, and emerge as an adult in January thru April. Eggs are laid in the stream in the colder winter months, larvae hatch and feed on the allochthonous detritus found along the stream bottom. Allocapnia are univoltine, which means that they produce only one brood per season. During the spring and summer the larvae remain in diapause, a form of hibernation, in the
substrate of the stream (Hilsenhoff 1995).

  • Present
  • Active
  • Larvae present and active

The time of year you would expect to find Illinois Stonefly present, active, and larvae present and active in New York.

Similar Species

  • None (Allocapnia curiosa)
    Allocapnia illinoensis is considered a northern relative of this species.
  • None (Allocapnia maria)
    Allocapnia illinoensis is considered a northern relative of this species.
  • None (Allocapnia pechumani)
    Allocapnia illinoensis is considered a northern relative of this species.

Illinois Stonefly Images


Illinois Stonefly
Allocapnia illinoensis Frison, 1935

  • Kingdom Animalia
    • Phylum Arthropoda (Mandibulates)
      • Class Insecta (Insects)
        • Order Plecoptera (Stoneflies)
          • Family Capniidae

Additional Resources


Frison, T.H.. 1929. Fall and Winter Stoneflies, or Plecoptera, of Illinois. Schnepp and Barnes Printers, Springfield, Illinois.

Hilsenhoff, W.L.. 1995. Aquatic Insects of Wisconsin: Keys to Wisconsin Genera and Notes on Biology, Habitat, Distribution and Species. Publication Number 3 of the Natural History Museums Council. University of Wisconsin, Madison.

Myers, Luke, Timothy Mihuc, and Boris Kondratieff. 2010. Draft report: Mayflies (Ephemeroptera), Stoneflies (Plecoptera), and Caddisflies (Trichoptera) of the Upper Hudson, Lake Champlain, and Northeastern Lake Ontario watersheds (New York State): A baseline inventory with management considerations for SGCN and other rare and possibly imperiled species.

NatureServe. 2021. NatureServe Explorer: An online encyclopedia of life [web application]. NatureServe, Arlington, Virginia. Available (Accessed: June 21, 2021).

New York Natural Heritage Program. 2024. New York Natural Heritage Program Databases. Albany, NY.

New York State Department of Environmental Conservation. 2015. State Wildlife Action Plan SGCN Stoneflies. Available at:<>{Accessed 21 June 2021].

Ross, H. H. and W. E. Ricker. 1971. The classification, evolution, and dispersal of the winter stonefly genus Allocapnia. Illinois Biological Monographs 45: 1-166.


About This Guide

This guide was authored by: Lutz, Colleen M.

Information for this guide was last updated on: June 23, 2022

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Allocapnia illinoensis. Available from: Accessed April 16, 2024.