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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.

Lateral view of a Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.
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 Ephemera blanda

Where & when

This species has a tiny range in southern Appalachia.

In 8 records from GBIF, adults of this species have been collected during July (50%), June (25%), and May (25%).

In 2 records from GBIF, this species has been collected at elevations of 2372 and 2559 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

Body length: 13–14 mm
Wing length: 12–12 1/2 mm

Summary: A yellowish brown species, the wings having very small dark spots only, in place of the usual wide dark blotches.

Head yellowish brown; vertex dark red-brown; eyes slate-grey, upper portion paler than lower; ocelli pearl-grey, widely black-ringed at base. Basal joints of antenna cream-colored, black at apex; filament pale grey. Pronotum yellow in median area; posterior and lateral margins creamy; a longitudinal black stripe on each side, beyond which is an outer red-brown area. Mesonotum dark red-brown, its anterolateral margins narrowly pale; median line may be narrowly pale; other margins darker brown. Metanotum deeper red-brown. Pleura yellowish with brown markings. Sternum light yellowish brown; posterior of prosternum dusky, areas above anterolateral portion of mesosternum brown. Coxa, trochanter, femur and tibia of fore leg yellowish to yellowish brown, tibia often paler in basal half; apex of femur, and base and apex of tibia, rather widely black-brown. Tarsus greyish, joining blackish grey. Middle and hind legs creamy white, claws greyish.

Costal margin of fore wing tinged with purplish brown, rather deeper in subcostal space. Cross veins in basal costal and subcostal spaces margined with dark brown, but less prominently than in Ephemera varia. About 10 basal costal cross veins, about 20 beyond the bulla; the latter considerably anastomosed in area halfway to apex of wing. Wing clear except for a very small purplish cloud extending downward from bulla for 3 to 6 spaces, very narrow, often not covering two cross veins; another small cloud in fork of posterior branch of radial sector, a third at basal end of long median intercalary. No other veins margined at all prominently, no other clouded areas. Main longitudinal veins of costal margin yellowish brown, other longitudinal brownish, very pale in anal area; principal cross veins brown. Veins on costal margin of hind wing yellowish, all others colorless. Outer margin of hind wing narrowly yellowish.

Abdomen pale yellowish, segments 8-10 opaque, and tinged with reddish yellow. Irregular purplish grey lateral spots on tergites 1 and 2. On tergites 3-9, a pair of longitudinal curved black lines on each side of median area, coalescing on 9; between these and pleural fold, a small brownish blotch; on 7-9, a pair of submedian streaks between the lateral pairs. A black spot on pleural fold at anterior margin of each tergite, and an irregular blackish line above it from posterior margin. Sternites 3-9 each with a single black penciling on each side of median line; 2 small median dots on sternite 1; mid-ventral line largely blackish, on sternite 9, and a small round dark dot on each side of this, anteriorly. Forceps base brown; forceps greyish; second joint of forceps relatively longer than in Ephemera simulans. Tails olive brown, joinings dark brown; in some areas, alternate joining only are darker.

Distinguished from other species by the lack of dark blotches in fore wing: otherwise, rather close to Ephemera varia.

Male Spinner

Described in Needham et al (1935) as Ephemera triplex
Body length: 11 mm
Wing length: 10.5–11 mm

A rather small pale species; wings largely pale, with purplish bullar stripe and two other small clouds only.

Head yellowish; frontal shelf hyaline, frontal portion of carina purplish; basal joints of antenna purplish brown at apex. Vertex tinged faintly with reddish brown, and with purplish shading near bases of ocelli, which are dark-ringed. Thorax light yellowish brown; a broad purplish black discontinuous stripe on each side of pronotum, the posterior margin narrowly same color, pale at median line. Mesonotum tinged with reddish brown, on postero-lateral areas; a purplish black V-shaped marking anterior to scutellum. Purplish transverse marks on metanotum. Pleura with reddish brown streaks and triangle anterior to middle leg, often a streak anterior to hind leg. Fore leg light reddish brown; apex of femur, base and apical third of tibia, basal tarsal joint and tarsal joinings, purplish brown; each tarsal joint darker in apical portion. Middle and hind legs yellowish, coxae and trochanters largely reddish brown, as are apex of femur, base and apex of tibia, and tarsal joinings.

Wings hyaline; faint yellowish brown tinge in stigmatic area of fore wing, otherwise pale. Costa, subcosta and radius of fore wing yellowish, all other longitudinal veins silvery white. Cross veins of fore wing, except in anal region, purplish black, rather fine, those of first three costal spaces and a few in disc, narrowly dark-margined. A curved stripe at bulla, extending backward to space above media; slightly wider in third space and at fork of posterior branch of radial sector. A small cloud posterior to this on media, nearer the margin; another at base of median intercalary. Basal subcostal cross veins of hind wing faintly yellowish, all other veins colorless.

Abdomen pale yellowish white; tergites with dark longitudinal pencilings as in E. blanda; often with crescent-shaped lateral blotches bordering outer stripe. Lateral portion of posterior margin of each tergite and sternite narrowly purplish. Sternites marked as in blanda. Outer margin of forceps base may be marked with purplish. Genitalia quite similar to Ephemera varia and Ephemera blanda; 2nd joint of forceps less bowed than in Ephemera varia. Tails yellowish white, joinings purplish brown; in places, alternate joinings wider. Female largely pale yellowish; markings as in male, but less distinct; thorax and legs paler.

Start a Discussion of Ephemera blanda


  • Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.
  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Ephemera blanda

Species Range
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