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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 Fallceon quilleri

Where & when

In 14 records from GBIF, adults of this species have been collected during September (21%), April (21%), August (14%), June (14%), July (14%), May (7%), and March (7%).

In 118 records from GBIF, this species has been collected at elevations ranging from 740 to 11401 ft, with an average (median) of 4938 ft.

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

Described in Needham et al (1935) as Baetis quilleri
Body length: 4-5 mm
Wing length: 5-5.5 mm

Abdominal tergites 2-6 of male imago deep olive brown; genitalia of the Baetis intercalaris type; hind wing with curved costal projection as in Centroptilum, and with cross veins between 2nd and 3rd vein.

Head and thorax of male deep blackish brown. Turbinate eyes (dried) large, deep reddish brown. Pleura largely paler reddish brown. Fore and middle legs missing. Hind femur pale smoky brown; tibia and tarsus pale yellowish white. Wings hyaline, venation pale. 8-9 cross veins in stigmatic area of fore wing; somewhat aslant, complete, with faint granulations between them. Marginal intercalaries well developed; a single one only in the first interspace. Hind wing much as in Dr. Dodds’ description, but with traces of one or more cross veins between veins 1 and 2, as well as a single well-defined one between veins 2 and 3 (see fig. 163). A faint marginal intercalary between veins 2 and 3, not seen in the female specimen. Abdominal tergites 2-10 deep olive brown, the basal ones semi-hyaline, posterior ones semi-opaque. Traces of darker oblique submedian dashes from the anterior margin of each tergite; at the end of each dash is a small dark dot. Sternites paler, yellowish olive, each with a distinct dark oblique submedian dash and dark dot near center of sternite on each side. Posterior margins of all segments opaque or slightly darkened, so that the abdomen appears annulate. Each spiracle marked with a small dark dot; a dark dash just above the spiracular line, which is faintly outlined in black. Tails missing. Genitalia imperfect, but apparently of the intercalaris type, quite similar to B. erebus (now a synonym of Fallceon quilleri).

Described as B. endymion

Body length 5 mm, wing length 5-5.5 mm

Abdominal tergites 2-6 of male imago semi-hyaline, yellowish to light olive brown; genitalia of the Baetis intercalaris type; hind wing of the quilleri type, three veins present.

Head light red-brown. Turbinate eyes moderate in size; in alcoholic specimens, pale orange with purplish shading. Thorax darker reddish brown; intersegmental areas of pleura paler; sutures of mesonota and metanota blackish; scutellum rather paler reddish brown. Femur and tibia of fore leg and femora of middle and hind legs yellowish, with faint reddish brown shading especially at each end; other joints pale yellowish white. Wings hyaline, venation pale; a small reddish brown spot at extreme base of each wing. A small opaque whitish cloud in the stigmatic area of the fore wing; about 8 cross veins, somewhat aslant, often incomplete at the subcosta; granulations present. Marginal intercalaries rather well developed; one or two in the first interspace. Hind wing relatively shorter and wider than in B. quilleri (now a synonym of Fallceon quilleri) (see fig. 163). Costal projection strongly curved, often wide at base. Third vein ending just beyond middle of hind margin; very faint traces of incomplete cross veins in each of the three spaces. Usually one intercalary between veins 2 and 3 (cross veins and intercalary, not shown in figure).

Abdominal segments 2-6, and basal half of 7, semi-hyaline; yellowish to light olive brown; sternites only slightly paler than tergites; posterior margins narrowly opaque whitish. Faint traces of a hyaline submedian streak on each side of middorsal line, and of short oblique streaks from the anterior margin of each sternite. Spiracular area and spiracles prominently outlined by a blackish geminate line, from which arise lateral branches to each tergite and sternite. Apical half of segment 7, and segments 8-10 opaque, light reddish brown, posterior and lateral margins somewhat brighter reddish brown. Forceps pale red-brown basally, tips whitish. The rounded projection or tubercle on the inner apical margin of the basal forceps joint either entirely wanting or very poorly developed. Distal forceps joint long, fully half the length of the third joint (in one paratype, more than half as long). Two lobe-like processes (penis lobes?) project from the apical margin of the forceps base, between the basal joints of the forceps. Tails whitish; basal joinings narrowly reddish or purplish brown, other joinings opaque whitish.

Described as B. erebus

Body length 4.5-5 mm, wing length 5 mm

Abdominal tergites 2-6 of male imago dark red-brown, semi-hyaline; genitalia of the Baetis intercalaris type; hind wing of the quilleri type.

Head and thorax deep blackish red-brown. Turbinate eyes moderately large, but slightly smaller than in B. quilleri (now a synonym of Fallceon quilleri); orange-brown. Intersegmental areas of pleura paler red-brown. Fore leg wholly light reddish brown, tarsus slightly paler. Middle and hind legs yellowish; tarsi and sometimes bases of tibiae tinged faintly with reddish brown. Wings iridescent, hyaline; venation light red-brown; a small reddish brown spot at base of each wing. Small opaque whitish cloud in stigmatic area of fore wing. 5-8 stigmatic cross veins, somewhat aslant, incomplete toward the subcosta; granulations present between them. Marginal intercalaries rather short; none in the first interspace. Hind wing of the quilleri type, but relatively longer than in that species; costal projection rather fish-hook-like. Third vein ends just beyond middle of hind margin. Between veins 2 and 3 is a well-developed intercalary. Traces of cross veins in each of the three spaces, most evident between costal margin and 1st vein (see fig. 163).

Abdominal segments 2-10 rather dark reddish brown; segments 2-6 semi-hyaline, 7-10 semi-opaque; sternites only slightly paler than tergites. Posterior and lateral margins of tergites, and median posterior margins of sternites, narrowly darker and opaque. Traces of a pale mid-dorsal line and of short oblique darker dashes at the anterior margin of each tergite. Spiracular line and spiracles faintly outlined in dark brown. Lateral areas of sternites next to pleural fold, and in some specimens a similar area on the tergites paler, hyaline. Tails rather dark red-brown basally, the distal half whitish; joinings opaque. Forceps red-brown basally, tips yellowish. A tubercle at inner apical margin of basal forceps joint only slightly developed; inner margin of first and second joint irregular, roughened; distal joint very long, more than half the length of the third joint. Between the forceps bases are two small lobe-like projections (perhaps penis-covers): see fig. 164.

Female Spinner

Described in Needham et al (1935) as Baetis quilleri
Body length: 4 mm
Wing length: 5 mm

Female somewhat paler reddish brown; abdominal sternites yellowish; tails yellowish, the joinings distinctly reddish brown. Dr. Dodds’ description, of the female only, is mainly diagnostic of the hind wing. Of this he says: “Narrow, with prominent curved humeral point, three longitudinal veins; first and second distinct and arising close together, but not from a common stalk; third faint and near the hind margin, where it ends at about three-fourths length of wing. There are two faint cross-veins between second and third longitudinal veins.”

Start a Discussion of Fallceon quilleri


  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Fallceon quilleri

Species Range
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