Small Winter Stonefly or Snowfly: A Good Sign

What kind of bug?
December 15, 2009
These bugs are hanging around our doorways, usually on the porch ceiling and they drop down on you when you walk outside. They are even out when the temp goes below freezing. They started about the first of November and are still here. What are they and how do I get rid of them? Thanks,
Dan Hoffer
Southwestern Pennsylvania

Winter Stonefly or Snowfly
Small Winter Stonefly or Snowfly

Dear Dan,
We are very excited to receive your letter, and we think it may make an excellent candidate for our Bug of the Month for January.  This is a Small Winter Stonefly in the family Capniidae, commonly called a Snowfly.  According to BugGuide, the  “family is distributed throughout much of North America but many species have restricted geographic ranges, and are endemic to relatively small areas
” so we are reluctant to try to identify the species, or even the genus.  It may also be a Winter Stonefly in the family Taeniopterygidae, also called a Snowfly and also depicted on BugGuide.  We will contact Eric Eaton to see if he can be more specific.  BugGuide also indicates:  “The defining need of winter stonefly nymphs is for very high levels of oxygen in the water. Warm temperatures, excessive organic matter, and many pollutants all reduce oxygen levels. The result: they’re only active in the coldest part of the year and are very sensitive to pollution.  Their main interest to humans is as an indicator species: you can tell that water is unpolluted if stoneflies live there. They also provide food for trout – though not as much as species active when trout are themselves more active in warmer parts of the year.

Winter Stonefly or Snowfly
Small Winter Stonefly or Snowfly

Confirmation from Eric Eaton
You are correct with the family, Capniidae, known as “small winter stoneflies.”  The genus is probably Allocapnia, but I am not an expert in aquatic insects and can’t be totally certain.  The presence of large numbers of these should be taken as a “good” sign!

2 thoughts on “Small Winter Stonefly or Snowfly: A Good Sign”

  1. I believe I have stoneflies all over the outside of my house flying in the snow and everywheres. How do I get rid of them?


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