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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
Baetis

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 Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington
Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
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 varia (Yellow Drakes)

Female Ephemera varia (Ephemeridae) (Yellow Drake) Mayfly Dun from Aquarium in New York
This is an excellent hatch of a different character than its Ephemera brethren. Rather than emerging in a flurry of activity within a week, the Ephemera varia hatch may last for more than a month in a single place.

Where & when

Time of year : Mid-June to mid-August, usually best in July

Adults of this species begin to show in mid-June in the Pennsylvania mountain ranges. The Catskills start a week or so later and hatches can be found in that region through early August. Farther north, and in the Upper Midwest, the hatch begins in mid-July and lasts into mid-August.

Some authors say this hatch is more important in the Midwest than in the East.

In 46 records from GBIF, adults of this species have mostly been collected during June (57%), July (26%), May (9%), and August (7%).

In 8 records from GBIF, this species has been collected at elevations ranging from 341 to 2723 ft, with an average (median) of 1951 ft.

Species Range

Hatching behavior

Time of day : Dusk

Habitat: Riffles, runs, and pools alike

Water temperature: 64-71°F

Yellow Drakes drakes take a long time and make a lot of commotion trying to get off the water. Their imitations are effective.

Several authors have remarked on the wide range of habitats from which this species will emerge. They apparently show no preference.

The hatch is best on cool, dry days. On cloudy days, according to Swisher and Richards in Selective Trout, the duns may emerge all day long. This behavior does not seem to be as prevalent as it is in Ephemera guttulata.

Spinner behavior

Time of day: Late evening to dusk, sometimes later

Habitat: Riffles, possibly elsewhere

The spinners return to the stream the day after they emerge. The females are reported to ride the water to oviposit, initially in the upright or semispent positions. However, I have also watched them repeatedly dip to the surface to lay eggs and rise back to knee height. Caucci and Nastasi in Hatches II recommend carrying both spent and semispent imitations for the females. The males fall completely spent.

There is some disagreement between authors about the precise spinner fall timing. It is generally late in the evening and may occur in the dark. I have encountered sporadic females ovipositing more than an hour before dark, and later I saw many more spinners in the air near the treetops.

Nymph biology

Current speed: Slow to medium

Substrate: Silt or sand and gravel

Like Ephemera simulans, these burrowers are at home in deposits of sand and fine gravel in freestone streams. This accounts for their good populations throughout the East. They also do well in silt like the Hexagenia mayflies. They usually mature in one year but may take two.

Ephemera varia Fly Fishing Tips

Don't let the common name of this species fool you into fishing a yellow-bodied fly. As my pictures show and other authors have pointed out, these mayflies have a creamy off-white body color. The duns are the same color as the spinners.

According to Knopp and Cormier, trout may fill up on nymphs during the hatch and leave the duns and spinners untouched.

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: 11 mm
Wing length: 12 mm

A rather pale species; fore wing tinged with brownish except in anal region, hind wing pale; no dark blotch in apical third of wing beyond bullar stripe.

Frontal portion of head reddish, carina black; basal antennal segments black apically, filament brownish, tips pale. Vertex red-brown, blackish between and at bases of ocelli. Thoracic notum light red-brown. A wide blackish longitudinal stripe on each side of pronotum. Mesonotal scutellum pale; dark brown area anterior to this; middle portion of mesonotum paler yellowish, also a pale median line; anterolateral margins brown. Metanotum pale, with transverse dark band near center. Pleura yellowish; red-brown oblique streak before middle and hind leg. Sternum pale yellowish, anterior portion of mesosternum marked with brown. Coxa and trochanter of fore leg yellowish; femur rather olive brown, yellowish at base, apex darker; base and apex of tibia widely brown, remainder yellowish, apical half brown-tinged; tarsus yellowish brown, short basal joint, apical half of distal joint and all joinings, dark brown. Middle and hind legs creamy white, claws faintly tinged with brownish.

Wings hyaline; fore wing tinged with brownish except in anal region and near base, where wing membrane and veins are pale or colorless; stigmatic area most deeply tinged. Longitudinal veins yellowish to yellow-brown. Cross veins blackish, those of basal costal and subcostal spaces margined narrowly with dark brown, many in the disc with wider marginings. A wide dark purplish band at bulla, slightly curved, and extending backward as far as space above anterior branch of media, wide enough to cover three cross veins. Posterior to this and nearer the margin, a smaller dark purple cloud; another at basal end of long intercalary of media. No cloud in apical third of wing beyond bullar stripe, though a few cross veins in third space are margined. Hind wing pale; costa and subcosta yellowish, basal cross veins in these spaces pale purplish; all other veins colorless, none dark-margined. Outer margin may be faintly yellow.

Abdominal tergites largely purplish grey; lateral margins, postero-lateral angles and mid-dorsal area pale yellowish white. On tergites 2-9, a pair of purplish black oblique submedian streaks extend backward and laterad from anterior margin on each side, conjoined posteriorly; inner of these not extending beyond middle of tergite, outer a little longer. Between these and along outer margin, whitish spaces. Blackish markings along pleura much as in Ephemera blanda. Posterior margins of tergites, and middle portion of sternites, dark purplish. Sternites pale yellowish white. A black longitudinal streak on each side, and a dark mid-ventral streak on sternites 8 and 9, as in Ephemera blanda. Forceps base yellowish brown, forceps yellowish; second joint longer than in Ephemera simulans; penes rather narrower (fig. 82). Tails yellowish to greyish yellow, joinings dark brown.

The darker abdominal tergites and more extensive blotches in fore wing distinguish this species from the allied Ephemera blanda. Venter of abdomen paler, wings less extensively dark-margined, body paler than Ephemera simulans. Nymph shown in fig. 80.

Specimens of the Mayfly Species Ephemera varia

1 Female Dun
1 Female Spinner
1 Nymph

Start a Discussion of Ephemera varia

References

Mayfly Species Ephemera varia (Yellow Drakes)

Taxonomy
Species Range
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