The large and unassuming American Salmonfly is a water-loving, ecologically sensitive insect that occasionally plays opossum.
American Salmonflies are the largest North American stonefly and are most active from late spring to late summer. Like other members of the Stonefly family, the American Salmonfly is a useful bio-indicator. The aquatic larvae of the American Salmonfly live underwater during these early life stages and they are extremely sensitive to pollution. If the water is laced with chemicals, the larvae will die. Hence, the sight of many adults means the water source and the ecosystem it supports are healthy and clean. For fishermen, the sight of American Salmonflies is most welcome.
Adults do not eat and have short life spans of less than a month. They are long and slender with dark wings that close tightly around their bodies. Their black eyes are bulge out of the sides of their head. A dark pronotum ('neck collar') is bordered in bright orange at both ends and a fading orange line that almost connects both ends. Long, black antennae and legs resemble those of beetles. They rest on rocks, reeds, and branches near or above water, waiting for opportunities to reproduce. If adults are threatened, they can release a chemical irritant from their legs in hopes of dissuading an attacker. If that fails, they may play dead.
Females drop fertilized eggs into the water. There, they hatch and develop into larvae. Their diet consists of algae and other rotting plant matter underwater. They are an important food source for fish. Anglers, especially fly fishers, use living larvae as well as manufactured imitations as fish bait. Where there are Salmonflies, there are fish. Larvae look like little crustaceans, not flying insects. After several rounds of molting and growing, they eventually leave the water where they mature into winged adults, shedding their exuviae, or exoskeletons. These empty 'shells' are abandoned not far from the water's edge.
Scientific Name: Pteronarcys dorsata
Other Name(s): Stonefly
Size (Adult; Length): 31mm to 48mm (1.21in to 1.87in)
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.