Near the end of February, I had a call from Don Hamilton, resource specialist for the National Park Service (NPS) out of Milanvile, PA. It seems that during a sunny day when the temperatures approached the 30s, he was observing a stonefly hatch from Calkins Creek, which runs along the edge of the NPS property in Milanville. Not only were there stoneflies, but there were also some eastern bluebirds observed making a meal of these emerging stoneflies.

Winter stoneflies, of which there are 42 species in their genus Allocapnia, emerge from rivers and fast-flowing streams during February. They can be spotted as tiny winged insects on snow near river and stream banks. Stoneflies are bio-indicators of water quality. Because stoneflies spend one or more years in the water as a nymph, they will be present only in high-quality water that is adequately oxygenated.

On March 9, I took a trip up to the Milanville Ranger Station; it promised to be a pleasant, sunny day with temperatures in the 40s. No bluebirds were found on this day, but there were several juncos and black-capped chickadees that appeared by the stream bank and started ground feeding. Through binoculars, I could see that they were taking advantage of the stonefly emergence to grab some tasty morsels. There seemed to be adequate stoneflies for all the birds; in some areas, they made the snow appear as if pepper had been sprinkled on it. After a while at streamside, a few stoneflies used my head and neck for a perch.

As more ice melts on rivers and streams, more winter stoneflies will be evident, and you will likely see a few different species. The appearance of stoneflies invokes a feeling that winter is on the way out. Perhaps this can be expressed by the last part of a poem by Mary Dow Brine, “The Coming of Spring:”

The brook, grown weary of restraint,

Has burst its weakened bonds at last,

And rushing down the mountain-side,

Lends its fresh influence far and wide,

And Winter’s icy reign is past!