Snow Flies

02/07/2019
Story and photo by Gabrielle L. Wheeler

I bet when you read that title you thought this article had to do with the snow flying since we all know bugs aren’t out during the winter. However, there are a few insects that do appear during the cold months, sometimes spotted wandering around on top of the snow. Winter insects have unique adaptations that allow them to be active in the cold. But for me, the main question is – why bother?

Members of the genus Chionea, or snow flies, are relatives of crane flies and emerge in the cold of winter. With good observational skills and some luck, these insects can be spotted wandering on top of the snow in the dead of winter, mostly in wooded areas. One informational site I found stated their habitat includes that which was covered in glaciers in the last ice age, which would explain why they are found in the Finger Lakes Region. Adding to the strangeness of their favored season, they do not have wings. One speculation is that stone flies have evolved without them as it requires absorbed heat for an insect to get enough energy to fly, which snow flies may be lacking in the dead of winter. The location of their would-be wings on the bug’s body has also been repurposed and female snow flies use it to store eggs, which evolution may have favored as a positive trade-off regardless of the energy factor.

Another winter insect is the winter stonefly (Capniidae and Taeniopterygidae families), which have retained their wings even though they are seen mostly just wandering around on the snow. I get winter stoneflies in my woods, as well as have had a number in my house this winter. For a moment I assumed that some rogue female had laid her eggs in my house last year, but stoneflies pass through an aquatic nymph phase and I have no stream running through my house, so must be they are just getting in somewhere. Stoneflies pass through an incomplete metamorphosis, emerging as adults in the winter months. Nymphs of this insect are a favorite bait and lure for fly fishing.

Both snow flies and winter stoneflies produce an antifreeze in their bodies that helps prevent their cells from freezing, resulting in the ability to be coldblooded yet also active in the cold. What is the point though? While little is actually known about snow flies, we know snow flies lay their eggs at this time of the year, and winter stoneflies mate. It is possible that both are taking advantage of a season when there is diminished predation in exchange for experiencing a warm breeze on their wings.


Gabrielle Wheeler is a freelance writer from the heart of the Finger Lakes Region. On her parenting blog, aplaceforlittlesproutstogrow.com, she writes about tending to the whole child and parent. She also works in a local health center as an interpreter/patient navigator.