Quill Gordon
Epeorus pleuralis
NYMPH 2
Size: Body length of mature nymph (excluding tails) 9-12 mm
Body: Body shape flat: head as wide or slightly wider than thorax with eyes on top of head; body color grey/olive-tan to reddish-brown
Gills: Large, held out to sides, and overlapping
Tails: Two tails
Nymph Look Alikes 2
Other flat-bodied mayflies (Heptageniidae). Epeorus is unique in the family as the only eastern genus with two tails as nymphs.
DUN (SUBIMAGO) 3
Size: Body length: 9-12 mm
Body: Greyish-brown/olive-grey with slight to moderate banding on abdomen.
Wings: Well-developed front and hind wings; uniformly slate grey
Tails: Two tails
Additional images:
From Troutnut.com: http://www.troutnut.com/specimen/681
From Bugguide.net: https://bugguide.net/node/view/927410/bgimage
https://bugguide.net/node/view/921277/bgimage
https://bugguide.net/node/view/478896/bgimage
SPINNER (IMAGO) 3
Size: Body length: 9-12 mm
Body: Reddish brown with lighter banding
Wings: Well-developed front and hind wings; hyaline (clear)
Tails: Two tails
Additional images
From Troutnut.com:
male: http://www.troutnut.com/specimen/496
female :http://www.troutnut.com/specimen/682
From Bugguide.net: https://bugguide.net/node/view/305080/bgimage
Dun/Spinner Look Alikes 3
Other members of the family Heptageniidae, all with two tails as adults. E. pleuralis is the earliest to emerge, but other northeastern taxa, particularly some species of Rhithrogena may emerge as early as early May in Massachusetts. Rhithrogena duns and spinners tend to be larger than those of E. pleuralis, and the bodies of the Rhithrogena spinners are darker and more uniformly colored. Compare also the forewing vein patterns in the stigma area (top front of wing, just before it begins to curve back) of E. pleuralis and Rhithrogena. E. pleuralis has parallel crossveins in the stigma area, while Rhithrogena crossveins are crisscrossed. See photo above.
The hatching of another Heptageniidae mayfly, the March Brown (Maccaffertium vicarium), may also partially overlap with that of E. pleuralis, but the March Brown has barring on the wings as both duns and spinners.
HABITAT & DISTRIBUTION 3
Epeorus pleuralis nymphs are found in the swift water of riffles and rapids in streams and smaller rivers. They are abundant in some of the Deerfield River’s major tributaries, including the South and Green rivers. This species ranges across the northeastern United States.
Range map from flyfishingentomology.com: http://www.flyfishingentomology.com/NAMayflySpeciesDistributionMapQuery2.php?sn=Epeorus%20pleuralis
LIFE CYCLE - EMERGENCE 2
Epeorus pleuralis is known among anglers as the first mayfly hatch of the season in the northeast. Once water temperatures reach 50oF, emergence activity can be a regular mid-afternoon occurrence on waterbodies supporting good numbers of this species. E. pleuralis (and other species of this genus) emerge underwater. The nymphs crawl to the underside of rocks near the river’s margin to split their nymphal skins. The duns are said to struggle to the surface, obviating the potential effectiveness of a wet fly fished in this manner. Adults will return to the river two days later after having molted into spinners and mate over swift water again during mid-afternoon hours.
Massachusetts: April into May
Degree of difficulty 4
This table is meant to help users get an idea of how easy/hard it is to ID this species to any taxonomic level, and to give an idea of the characters (or features) that are important to accurately identifying a specimen. As a general guideline, these degree of difficulty levels translate to the type of effort needed to reliably ID a specimen to that taxonomic level, as long as the associated features are confirmed. Of coarse there will/may be exceptions to these general rules.
Eporus pleuralis
Taxonmoic level
Taxonomic Name
Feature
Degree of difficulty
Order
Ephemeroptera
Wing Shape
1
Family
Heptageniidae
Well developed larger hind wing /adult 2 tails
2.5
Genus
Eporus
Two tails,9-12 mm,Greyish-brown/olive-grey with slight moderate banding on abdomen
3.5
Species
pleuralis
Time of year April-may/two tails/ size beatids at the same time of year are smaller/ color-banding on abdomen
3
Degree of Difficulty
Degree of Difficulty
Description
1
Can be ID’d on the wing or water.
2
A specimen in the hand can be ID’d.
3
Can be ID’d by studying a decent photo of the specimen.
4
Can be ID’d by studying a captured & preserved specimen, usually under some magnification.
5
Proper ID requires study of preserved specimen under magnification, usually looking for some feature that can be difficult to confirm. Usually requires training or confirmation from a professinal.
Sources and Credits
- (c) Jerry Schoen, all rights reserved, uploaded by Jerry Schoen
- Adapted by Jay Aylward from a work by (c) Jerry Schoen, some rights reserved (CC BY-SA)
- (c) Jerry Schoen, some rights reserved (CC BY-SA)
- (c) Jay Aylward, some rights reserved (CC BY-SA)
