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Montana Field Guide

Montana Field Guides

Hyalite Snowfly - Isocapnia hyalita

Native Species

Global Rank: G4
State Rank: SNR

Agency Status


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General Description
Species within the Capniidae are small winter stoneflies. This family is one of the largest families in the order Plecoptera, containing some 300 species distributed throughout the Holarctic region, 25 species occur in Montana. As their name implies these species are generally cold-water stenotherms and hatch in late-winter through early spring. The adults emerging in the winter are often found walking around on the snow. Their closest relatives are the rolled-winged stoneflies (Leuctridae). Many species are endemic to small ranges, perhaps due to the family's tendency to evolve tolerance for cold (isolating populations in mountain valleys) and winglessness (inhibiting dispersal).

Range Comments
Rangewide, the species is known from the Rocky Mountains: Montana, Idaho, Colorado and Utah. Type locality in Hylite Creek, Gallatin County south of Bozeman
British Columbia, Alberta, Idaho, Montana (Lake & Missoula County). It is known from <30 EO's (most in Canada), mostly springs, seeps and small rheocrenes (NatureServe 2006). No map is available!!

Very little information exists about the ecology of this species (Baumann, Gaufin, and Surdick 1977). Reported that members of this species are found more likely in creeks, and are trophically shredder-detritivores.

Food Habits
Merritt and Cummins (1996) report that members of this family are trophically shredder-detritivores; eating large particulate organic materials such as detritus, leaves and plants.

Probably cold water stenotherms

Reproductive Characteristics
Adults are flying in a brief period April & May

Threats or Limiting Factors
Listed as a rare species when found, never abundant, but adults are rarely collected by biomonitoring agencies, thus few records exist!!!

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Citation for data on this website:
Hyalite Snowfly — Isocapnia hyalita.  Montana Field Guide.  .  Retrieved on , from