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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 Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington
This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
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 Neoleptophlebia temporalis

Where & when

Time of year : Late June through August

In 10 records from GBIF, adults of this species have been collected during June (50%), April (20%), August (10%), July (10%), and May (10%).

In 2 records from GBIF, this species has been collected at elevations of 7992 and 8500 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: 6 mm
Wing length: 7-8 mm

This is another brownish, pale-legged species with diffuse pale basal rings on the middle abdominal segments. Head and thorax brown above, with the sides and the terminal abdominal segments paler brown. Legs pale brown, whitish beyond the knees. Wings sub-hyaline with pale brown veins. Cross veins nearly obsolete in most of the costal space; single and straight and spaced well apart in the stigmatic region. The brownish rings upon segments 2-7 of the abdomen are very diffuse and ill defined and only slightly darker on segments 2 and 7 than on the intervening segments. The black of the spiracle is extended rearward in an R-shaped line covering the postero-lateral angle. The basal segment of the forceps is tapered to three-fourths its length. There is a wide V-shaped notch between the two penes. The sperm duct ends in a long straight, tubular process on the outer sides of which stands a long spirally twisted spine (see fig. 133).

This species differs from P. pallipes (now a synonym of Neoleptophlebia memorialis) in that the above mentioned spine lies in the same plane as the tubular process, not curving upwards as in that species.

Start a Discussion of Neoleptophlebia temporalis


Mayfly Species Neoleptophlebia temporalis

Species Range
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