Montana Field Guide

This is a small black stonefly in the family; Leuctridae. Like most of the species in the rolled-winged family, this species hatches early in the year often when snow is still on the ground, where they can be noticed quite easily crawling around along the banks of streams.

Emergence occurs from April through July (Baumann, Gaufin, and Surdick 1977). Hoppe (1938) and R. Newell (pers. comm.) found males and females in copula in mid-May at White Horse Mt, Washington and western Montana, respectively.

Adult male morphology: “Length to tip of wings 11 mm. Expanse 19 mm. General color dark brown. Head blackish, little wider than prothorax, covered with white pile; a transverse depressed area jut back of hind ocelli; the hind ocelli about three times as close to the eyes as to each other; antennae brown; maxillary palpi very large. Prothorax blackish brown, distinctly longer than wide; slightly narrowed behind; front margin rounded; sides straight, surface rugose, the rugosity black. Legs brown. Middle tarsal segment short; first tarsal segment of meso and metathoracic segments longer than third. Wings uniformly subhyaline with reddish or rusty tinge; veins brown. Abdomen brown. Cerci chitinized with a small black spur at the tip and a large black tooth at the base pointing upward” (Needham and Claassen 1925).

Ecology: This species inhabits creeks and small rivers but is most common in springs (Baumann, Gaufin, and Surdick 1977).

Merritt and Cummins (1996) report that members of this family are trophically shredder-detritivores; eating large particulate organic materials such as detritus, leaves and plants.

Ecology: This species inhabits creeks and small rivers but is most common in springs (Baumann, Gaufin, and Surdick 1977).

Emergence occurs from April through July (Baumann, Gaufin, and Surdick 1977). Hoppe (1938) found males and females in copula in mid-May at White Horse Mt., Washington.

Specific threats to Montana populations of P. utahensis have not been identified. In general, stonefly populations are affected by changes to aquatic habitat such as alteration of flow patterns, streambed substrate, thermal characteristics, and water quality. Alteration and degredation of aquatic habitats or water quality are the primary concern for Montana populations.