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Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

Dorsal view of a Zapada cinctipes (Nemouridae) (Tiny Winter Black) Stonefly Nymph from the Yakima River in Washington
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Mayfly Species Isonychia diversa (Slate Drakes)

Species Range

Physical description

Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.

Male Spinner

Body length: 9 mm
Wing length: 9 mm

A small brownish species, with pale wings and unique genitalia.

Head and thorax dark reddish brown, brightest on the notum; pleura somewhat paler. Fore femur dark red, becoming blackish at the apex. Tibia blackish. Tarsus pale reddish brown, the basal half of the first and second joints yellowish. Fore tarsus as long as the tibia. Middle and hind legs whitish; femora slightly tinged with reddish, claws pale smoky. Wings hyaline, venation wholly pale.

Abdomen smoky brown with a reddish brown tinge. Tergites 9 and 10 are dark red-brown, sternites 8-10 bright reddish. Middle sternites paler than tergites, somewhat translucent. Posterior margins of all segments conspicuously dark. Pleural fold pale at margin; above this pale line is a dark strip at the center, and a dark mark in the stigma. Mid-dorsal line pale, widened posteriorly. Dark brown submedian streaks margin it, and are in turn margined by paler translucent strips, and these by a darker line. Submedian streaks obscure basally, distinct apically. Postero-lateral angles dark brown; antero-lateral angles paler, translucent. Sternites marked as are the tergites, with a wider median line. Tails white, unmarked.

Forceps base reddish; deeply excavated on apical margin. Forceps pale. Penes reminiscent of Siphloplecton in their form. Wide and united at the base, they taper suddenly, but again curve outward to form more or less rounded apical lobes, separated by a V-shaped notch. Each has a slight indentation on the apical margin (see fig. 126). Second joint of forceps at least a third longer than the terminal joints combined. Basal joint rather long and slender.

Start a Discussion of Isonychia diversa


Mayfly Species Isonychia diversa (Slate Drakes)

Species Range
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