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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

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 Serratella micheneri (Little Dark Hendricksons)

Where & when

In 11 records from GBIF, adults of this species have been collected during July (45%), August (27%), June (18%), and September (9%).

In 9 records from GBIF, this species has been collected at elevations ranging from 1450 to 6325 ft, with an average (median) of 5056 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 Ephemerella micheneri
Body length: 6 mm
Wing length: 6 mm

A member of the serrata group (now a synonym of Serratella serrata); yellowish with brownish markings; tails white, joinings dark; two or three blunt processes on the apical margin of each division of the penes.

Eyes orange. Head yellowish shaded with brown. Thorax yellowish, with brownish black markings; a dark band and streak on the prothoracic pleura; scutum, scutellum and median line of mesonotum margined with dark brown; two lateral dark streaks and three median dots on metanotum. Two blackish streaks on the pleura anterior to the middle and hind legs; coxae black-marked; median areas of the prosterna and mesosterna outlined in black, ganglia of the mesosterna and metasterna darkened. Legs yellowish; fore tibia and tarsus pale smoky. A narrow reddish brown apical band on each femur. Claws and basal tarsal joints smoky. Wings subhyaline to hyaline; venation pale. A purplish streak on the membrane of the fore wing near the base, below the costa; a brownish spot at base of costa and subcosta.

Abdominal tergites brownish; 2-8 rather heavily shaded with reddish to olive brown laterally. Posterior margins pale; brownish black stigmatic marks; pleural fold pale. Sternites yellowish; ganglionic areas purplish black; a reddish brown streak or triangular area borders the pleural fold, on each side. Genitalia yellowish. Two or three blunt processes are present on the apical margin of each division of the penes (see fig. 156). Tails white, joinings purplish black.


Described in Needham et al (1935) as Ephemerella micheneri

Head and thorax of nymph smooth; maxillary palp rather well developed. Thoracic ganglia and the anterior margins of the prosterna and mesosterna blackish. Legs pale yellowish; a black spot at base of tarsus; apex of tarsus, and claw, blackish brown. 7 to 8 denticles on each claw. Dorsal spines present on tergites 2-8; short on 2 and 8, longest on 5-7. Extensions of abdominal segments and the postero-lateral spines short; no spine on segment 8. General color yellowish to yellowish brown, the basal and middle tergites shaded with black. Blackish lateral patches are often present on the middle tergites. Ganglionic areas of the sternites are darkened; a double row of curved brown marks is present on each side. Tails alternately yellow and brownish black.

Specimens of the Mayfly Species Serratella micheneri

3 Nymphs

Start a Discussion of Serratella micheneri


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

Mayfly Species Serratella micheneri (Little Dark Hendricksons)

Species Range
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