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American Springfly - Skwala americana
General Description
The Skwala is a colorful stonefly nymph that hatches in early spring when not many other insects are hatching, making it the first large, post-winter meal for trout, and good fishing for fisherman. The Skwala hatch begins as river waters begin to warm, usually the end of February, which provides a pre-runoff fishing opportunity. The Bitterroot River has become a favorite river for the skwala hatch, but many other large Montana rivers such as the Clark Fork River, Blackfoot, Smith, Yellowstone and Madison Rivers contains these insects in large enough numbers to make fishing the hatch worthwhile.
Phenology
The Skwala hatch begins as river waters begin to warm, usually the end of February and continues through April in dark canyon reaches that remain colder.
Species Range
Montana Range
Range Descriptions
Native
Observations in Montana Natural Heritage Program Database
Number of Observations: 29
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Food Habits
Merritt and Cummins (1996) report that members of the families, Perlidae and Perlodidae, are largely predators eating other aquatic invertrebrates, especially Diptera (Chironomidae and Simuliidae, midges and blackflies) and Mayflies.
Ecology
The Skwala hatch begins as river waters begin to warm, usually the end of February,
References
- Literature Cited AboveLegend:
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Cummins, K.W. and R.W. Merritt. 1996. Ecology and distribution of aquatic insects. Chapter 6, pages 74-86 in R.W. Merritt and K.W. Cummins (eds.) An Introduction to the Aquatic Insects of North America. Third Edition. Kendall/Hunt Publishing Company, Dubuque, Iowa. 862 pp.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Fraley, J.J. 1978. Effects of elevated summer water temperatures below Ennis Reservoir on the microinvertebrates of the Madison River, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 120 p.
- Glorvigen, T.H. 1972. The responses of insect communities in the East Gallatin River, Montana, to sewage effluents. M.Sc. Thesis. Bozeman, Montana: Montana State University. 24 p.
- Gustafson, D. L. 1990. Ecology of aquatic insects in the Gallatin River drainage. Ph.D. Dissertation. Bozeman, MT: Montana State University. 194 p.
- Stadnyk, L. 1971. Factors affecting the distribution of Stoneflies in the Yellowstone River, Montana. M.Sc. Thesis. Bozeman, Montana: Montana State University. 36 p.
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