Green stoneflies, or sallflies if you are an angler, are unusual in that most species in the family are green or yellow. They may be mistaken for recently emerged individuals of other stonefly families, but a few characteristics stand out: few crossveins on the wings, fairly long paired appendages on the abdomen (cerci), and a nearly oval pronotum with front corners broadly rounded, the prominent plate-like structure that covers the thorax. The adults fly mostly from May to August and are typically seen resting on vegetation near water. The aquatic nymphs, who have been described as “slender and velvety” by Merrill A. Peterson, develop in streams and creeks. Most prey on aquatic invertebrates, but a few feed on algae.

Size: Adults 6 – 15 mm 

Photo by: Kristi DuBois on 8/12/22 in Mineral County, MT