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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.

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 Matriella teresa (Little Dark Hendricksons)

This is the only species of Matriella reported in North America. It has a western disribution and is of limited importance to anglers.

Taxonomic History

It was previously known and mentioned in some angling texts as Serratella teresa.

Where & when

In 1 records from GBIF, adults of this species have been collected during July (100%).

In 1 record from GBIF, this species has been collected at elevation of 3600 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.


Described in Needham et al (1935) as Ephemerella teresa
Body length: 5-8 mm

A species of the serrata group (now a synonym of Serratella serrata); seemingly very close to E. micheneri (now a synonym of Serratella micheneri). Dorsal abdominal spines present. Only the nymphal stage is known.

Head and thorax smooth. Maxillary palp wanting. Median line of pronotum elevated anteriorly, depressed posteriorly; bordered by lateral carinae. Legs pale; apices of joints reddish brown. 9-10 denticles on each claw. Thoracic ganglia darkened. A purplish line along the costal margin of the developing wing. Lateral abdominal extensions and postero-lateral spines only moderately developed. Dorsal spines present on tergites 4-7; short and furthest apart on 4; longer and subequal on 5-7. Gills borne on tergites 3-7. General color pale reddish brown; darker lateral patches present on tergites 4-8, and dark dots on 9. Sternites yellowish; ganglionic areas often darkened, and a row of dark lateral dashes on each side, as in E. serrata. Tails pale yellowish, with a whorl of dark reddish brown spines at each joining.

Described as E. cognata

Body length 7-8 mm

A member of the serrata (now a synonym of Serratella serrata) group. Head and thorax of nymph smooth; dorsal spines present; postero-lateral spines longer than in Ephemerella tibialis. Abdominal sternites of female with black lateral marks and darkened ganglionic areas.

Mandibles of nymph well developed. Maxillary palp vestigial, represented only by a minute stub. No head or thoracic tubercles, but a slight elevation on each side of the pronotum on the posterior margin. Legs reddish brown; apex of tibia and a median tarsal band pale. 9 to 10 denticles on each claw. Gills present on tergites 3-7. Lateral extensions of abdomen, and postero-lateral spines, better developed than in the related species tibialis. True dorsal spines present on tergites 4-7; on 4 these are wider apart than elsewhere. General color dark reddish brown. Ventral abdominal markings consist of dark ganglionic blotches and a series of dark lateral streaks. Tails yellow at base, alternately brown and yellow beyond the middle. Tails of subimago white, joinings purplish black.

Start a Discussion of Matriella teresa


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

Mayfly Species Matriella teresa (Little Dark Hendricksons)

Species Range
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