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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 Setvena wahkeena (Perlodidae) (Wahkeena Springfly) Stonefly Nymph from Mystery Creek #199 in Washington
As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
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 Paraleptophlebia praepedita (Mahogany Duns)

This species may reinforce hatches of Paraleptophlebia debilis.

Where & when

Time of year : July through October

Preferred waters: Relatively large, warm trout streams

In Mayflies of Michigan Trout Streams, the Leonards report finding a single male adult of this species in late May. This is outside the range of emergence dates given by Knopp and Cormier in Mayflies: An Angler's Study of Trout Water Ephemeroptera .

In 23 records from GBIF, adults of this species have mostly been collected during May (39%), June (30%), and July (26%).

In 6 records from GBIF, this species has been collected at elevations ranging from 3 to 141 ft, with an average (median) of 23 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: 5 mm
Wing length: 5-6 mm

This is an all brown species without color pattern, with only varying depths of tint. Top of head and thorax and base of abdomen dark brown, with the sides and the middle of the abdomen and all the appendages paler brown. Fore legs darker than the others; all legs darker at the knees. Wings sub-hyaline with brown veins; costal cross veins few and faint, those of the stigmatic area short, simple and regular.

Abdomen paler on the middle segments darkening toward both ends. Spiracles indicated by minute and faint brownish dots. The 9th sternite is very long, one-half longer than wide, carrying the forceps far to rearward. The first segment of the forceps is divided by a basal constriction which sets off a sub-segment one-fourth as long as wide. Penes as long as the forceps, separated at half their length by a narrow, V-shaped cleft, flattened horizontally in their apical third and outcurving, and bearing a minute posteriorly-directed triangular tooth at the tip. At two-thirds of their length there arises a pair of reflexed spurs that curve outward and upward to rounded tips. These spurs are about one-third as long as the main segment of the forceps (see fig. 134). Tails nearly uniform pale brown.

Start a Discussion of Paraleptophlebia praepedita


Mayfly Species Paraleptophlebia praepedita (Mahogany Duns)

Species Range
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