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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 Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington
This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.
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 adoptiva (Blue Quills)

This is the best Spring hatch after the Quill Gordons (Epeorus pleuralis) but before the Hendricksons (Ephemerella subvaria) in most parts of the East, although it can overlap with both. The Blue Quills are small mayflies (hook size 16-20) but they can hatch in incredible numbers at a time when eager trout are just beginning to look to the surface after a hungry winter.

Where & when

Time of year : April through early June

The hatch begins in early April in the southern Appalachians. By late April or early May it is in Pennsylvania, and it peaks in the Catskills in early May. By late May it has moved into the Upper Midwest and the Adirondacks, where it may linger through early June. The peak hatching lasts nearly a week in most places.

One source, Mayflies of Michigan Trout Streams, says the hatch may last until July 8th, but I have found no other accounts of such late adoptiva hatches.

In 4 records from GBIF, adults of this species have been collected during April (75%) and June (25%).

In 2 records from GBIF, this species has been collected at elevations of 443 and 896 ft.

Species Range

Hatching behavior

Time of day : Late morning through afternoon, peaking at midday

Water temperature: 50�F

Caucci and Nastasi in Hatches II say that trout feed exceptionally well on these nymphs during the hatch, and they recommend fishing nymph imitations (both deep and floating) with an upstream dead-drift. However, the duns should not be ignored, because they may ride the surface for a long time before flying away.

The hatch can be strongest on cold, dark, even snowy days.

Spinner behavior

Time of day: Midday

Habitat: Riffles

The females oviposit by repeatedly diving and dipping the tips of their abdomens into the water.

The first spinners appear a few days after the first duns, and they may persist for up to a week after the duns are done emerging.

Nymph biology

Current speed: Medium is best; slow is good; slow microhabitat in fast stretches are okay

Substrate: Gravel, detritus

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: 7 mm
Wing length: 7-8 mm

This is a blackish species with a brown abdomen that is only a little paler in the middle. Top of head and thorax shining black, only the sutures on the sides paler; dorsum of the first abdominal segment also blackish. Legs brown including the tarsi, paler brown beyond the knees. Wings sub-hyaline with brown veins and darker brown wing roots. Costal cross veins faint and rather numerous; those of the stigmatic region long, sinuate and crowded, but little conjoined. The abdomen is nearly uniform brown, only the base of segments 3-5 showing a suggestion of pale rings; and the apical segments are only a little darker on the dorsum. Forceps yellowish brown; the 2nd joint twice as large as the 3rd. Penes appressed, half as long as the first joint of the forceps. The sperm ducts terminate before the apex between a rounded inner lobe and an outer triangular tooth that is turned sharply laterally; below this the outer margin of the penis is suddenly widened and the basal portion parallel-sided (see fig. 135). Tails uniform pale brown.

Specimens of the Mayfly Species Neoleptophlebia adoptiva

1 Male Dun
1 Male Spinner

1 Streamside Picture of Neoleptophlebia adoptiva Mayflies:

Start a Discussion of Neoleptophlebia adoptiva


Mayfly Species Neoleptophlebia adoptiva (Blue Quills)

Species Range
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