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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.

Dorsal view of a Sweltsa (Chloroperlidae) (Sallfly) Stonefly Nymph from the Yakima River in Washington
This species was fairly abundant in a February sample of the upper Yakima.
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 Drunella longicornis

Species Range


To determine whether a specimen of Drunella belongs to Drunella longicornis, use the Key to Species of Drunella Nymphs.

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 longicornis
Body length: 8-9 mm
Wing length: 8-9 mm

A species of the fuscata (now a synonym of Drunella walkeri) group; a very close ally of E. cornuta (now a synonym of Drunella cornuta). Hind femur rather longer relatively than in cornuta; tarsi and tails darker; pleural fold rather widely pale.

Head largely brown. Thorax dark olive brown dorsally. A round pale spot on each side of the median line of the pronotum, which is also pale laterally. A greyish streak anterior to the wing roots; pleura with paler markings. Fore femur yellowish brown, shaded with dark brown; tibia and tarsus dark brown, last tarsal joint paler brown. Femora and tibiae of middle and hind legs yellow margined with brown; tarsi dark brown, paler on the distal joints. Hind femur as long as tibia and tarsus combined. Wings hyaline, longitudinal veins pale yellowish brown; a brown spot at base of fore wing. Abdomen dark reddish brown dorsally; a pale submedian spot on each side of the mid-dorsal line, on the anterior margins of the middle tergites. Pleural fold rather widely pale. Tergites darker brown next to the pleural fold and on the posterior margins. Light yellowish brown ventrally; on each sternite a dark brown lateral streak lies next to the pleural fold. Postero-lateral spine on segment 9 longer than that of cornuta. Tails purplish brown. Third joint of forceps relatively shorter, and second joint less strongly bowed, than in E. cornuta; penes spread more widely at apex (see fig. 153).


Described in Needham et al (1935) as Ephemerella longicornis

Nymph distinguished from cornuta by the longer frontal horns and the longer and more curving tibial spine.

Nymph quite similar to that of E. cornuta. Light reddish in color, the thorax often checkered and mottled with contrasting light and dark areas. Abdomen rather lighter in color than thorax. Frontal horns very long and relatively straight; their length is more than half the width of the space between them (see fig. 151 b). Prominent spines on the anterior margin of the fore femur; its posterior margin almost straight. The ‘thumb’ of the fore tibia is longer than in cornuta, extending beyond the middle of the tarsus; it likewise curves outward sharply in its distal portion (see fig. 154). Postero-lateral spines of the abdominal segments are somewhat longer than in cornuta. Abdomen yellow ventrally, with a row of dark marks on each side, near the pleural fold. Sternites 2-8 hairy, also the posterior margins of the legs. Legs yellowish with indistinct reddish bands.

Start a Discussion of Drunella longicornis


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

Mayfly Species Drunella longicornis

Species Range
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