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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.

Lateral view of a Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.
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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Mayfly Species Neoleptophlebia mollis (Jenny Spinners)

This species often emerges together with Paraleptophlebia strigula and Paraleptophlebia guttata, and the combined effect can be a good fishable hatch. The latter two are much less famous than mollis, but Knopp and Cormier say they are more reliable.

Where & when

Time of year : Late May through August; best in June

This species begins to emerge soon after Paraleptophlebia adoptiva has finished.

In 11 records from GBIF, adults of this species have been collected during June (45%), July (45%), and May (9%).

In 4 records from GBIF, this species has been collected at elevations of 3, 69, 240, and 643 ft.

Species Range

Hatching behavior

Time of day : Late morning to midday

The duns ride the surface for a long time before flying away. The Leonards report in Mayflies of Michigan Trout Streams that trout feed heavily on Paraleptophlebia mollis duns.

Spinner behavior

Time of day: Late afternoon

The male spinners have a unique look: most of their abdominal segments are white.

Nymph biology

Current speed: Slow

Environmental tolerance: Tolerant of warm water

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

Described in Needham et al (1935) as Paraleptophlebia mollis
Body length: 8 mm
Wing length: 8 mm

This is a white-winged, white-legged, white-tailed species with dark brown thorax and brown tipped white abdomen. Head, thorax, and basal segment of the abdomen brown, darker above and beneath, with paler sutures at the sides. All appendages white. Wings white with whitish veins and with scarcely any darkening of the stigmatic area. Costal cross veins almost undiscoverable except in the stigmatic area where they are rather crowded, strongly aslant, sinuous, and sometimes forked. Segments 2 to 7 of the abdomen entirely translucent white, with no markings on either ganglia or spiracles. Segment 8 is pale brown, 9 and 10 are somewhat darker brown. Forceps and tails white. Penes pale brown, separated by a narrow cleft; each tip bears externally a thin, flat, triangular lobe that terminates laterally in a sharp, upcurving thorn-like point (see fig. 133).

Specimens of the Mayfly Species Neoleptophlebia mollis

1 Male Dun

Start a Discussion of Neoleptophlebia mollis


Mayfly Species Neoleptophlebia mollis (Jenny Spinners)

Species Range
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