Long, slender Common Stonefly adults are often found near streams where they once swam, avoiding trout and other hungry fish.
The Common Stonefly is a member of the Perlidae family. Together with Caddisflies and Mayflies, the presence of Stoneflies suggests clean streams and water. The adult looks different from the juvenile. Adult Common Stoneflies are a dark brown or olive-brown color. The wings overlap each other over the body and are covered in dark veins. The base of the antennae are yellow as is the lower part of the head. Between the 'neck' and the wings are two more yellow spots (one near each shoulder). A look at the body under the wings reveals two tails that are generally covered by the wings from overhead.
Offspring are called naiads and they look more like tiny crustaceans than insects. Females lay eggs on or just above the water's surface and die soon after, sometimes on the water. The hatched naiads spend their life underwater feeding and growing. Once they are ready to become adults, they head to land and metamorphosize into winged adults, leaving their empty exoskeletons behind. Because naiads of Stoneflies are eaten by trout, anglers tend to monitor the presence and life stage of a local population of Stoneflies to better time their fishing expeditions. The area where many naiads leave the water can be a popular feeding spot for trout, where the fish feed on naiads that swim poorly. These emergence sites are therefore popular fishing holes for anglers. Synthetic replicas of the naiads can serve as bait.
Common Stoneflies are most active in the summer and may be more visible in the western provinces and states during the day. Eastern populations may be more active at night.
Scientific Name: Paragnetina media
Other Name(s): Embossed Stonefly
Size (Adult; Length): 20mm to 60mm (0.78in to 2.34in)
Note: An insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above as they are driven by environmental factors (such as climate change), available food supplies and mating patterns. Grayed-out selections indicate that the subject in question has not been reported in that particular territory. U.S. states and Canadian provinces / territories are clickable to their respective bug listings.