Mayfly Species Matriella teresa (Little Dark Hendricksons)

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.