Alderflies

Overview

Alderflies (order Megaloptera) are large, sluggish insects often misidentified — larvae resemble small hellgrammites, and adults get mistaken for oversized dark caddisflies. Adults appear in early summer, dark brown to charcoal, with long antennae and smoky wings held roof-like over the body. Weak fliers, they spend most of their short adult lives clinging to streamside vegetation, logs, and rocks, and frequently fall onto the water when disturbed or mating. Swarming adults over the water are a strong cue to fish an alderfly or hellgrammite-style pattern tight to banks and slower edges.

Larva

Larvae are dark brown to black, thick-bodied, and slightly flattened, with short lateral filaments along the abdomen. They live buried in silt, leaf litter, and soft substrate in ponds and slow-moving rivers, developing over one to two years as aggressive aquatic predators. Hook sizes: 10 to 14.

Dry/Adult

Adult patterns imitate a struggling insect drifted tight to cover. Hook sizes: 12 to 16.

Curated by the IdentaFly fly fishing team.