The little-known mayfly Siphlonurus autumnalis McDunnough (Ephemeroptera: Siphlonuridae) was collected from several locations in its floodplain habitats along the Middle Fork of the Flathead River in western Montana. To confirm identification, nymphs were reared along with an associated species, S. occidentalis Eaton (Ephemeroptera: Siphlonuridae). Adults emerged from 6 September until 16 October. Habitats are described and the first photos of the 2 sexes are provided.
Newell, Robert L. and Anderson, Michelle L.
"Note on the occurrence of Siphlonurus autumnalis (Ephemeroptera: Siphlonuridae) in a Montana spring brook,"
Western North American Naturalist: Vol. 69
, Article 15.
Available at: http://scholarsarchive.byu.edu/wnan/vol69/iss4/15