Eastern Sulphur/Pale Evening Dun
Ephemerella dorothea
NYMPH 13
Size: 5 to 7 mm
Body: Rounded in cross section (not flattened); color olive brown, red brown, to tan-brown
Legs: Light brown/tan with medium brown banding
Tails: Three tails
Nymph Look Alikes 14
Without magnification, nymphs of the genus Ephemerella can be difficult to identify to species. The three common Ephemerella species in central New England include E. subvaria, E. invaria, and E. dorothea. Both E. subvaria and E. invaria are larger than E. dorothea when mature, and E. dorothea lacks short, paired spines present on the abdominal segments of both E. subvaria and E. invaria. Furthermore, nymphs of other genera within the Ephemerellidae family generally resemble E. invaria in shape, size, and coloration. When possible, mature specimens should be collected for more reliable identification under magnification.
DUN (SUBIMAGO) 14
Size: 5 to 8 mm (males slightly smaller than females)
Body: Yellow to cream
Wings: Light grey
Tails: Three tails, light brown and barred
SPINNER (IMAGO) 14
Size: 5 to 7 mm
Body: Males have white abdomens with yellow to orange yellow thoraxes; females are cream to yellow cream with a light brown cast on the abdomen and orangish yellow thorax.
Wings: Clear wings (hyaline)
Tails: Three tails
Dun/Spinner Look Alikes: 14
Ephemerella invaria is similar to E. dorothea, but E. dorothea is smaller (5-7 mm versus 8-10 mm).
HABITAT & DISTRIBUTION 14
Ephemerella dorothea is one of the more common mayflies in trout streams and small rivers across the eastern United States. Able to tolerate a range of temperature and flow conditions,E. dorothea is widespread and often abundant in eastern streams. Nymphs occur in a variety of habitats, from slow-flowing pools and runs to fast riffles, although they will tend to be most numerous in medium- to fast-flowing reaches.
LIFE CYCLE - EMERGENCE 14
Anglers eagerly await the “sulphur” hatches of early summer. Both E. invaria and E. dorothea are known by this common name. In addition to the size difference between the two species (see “Lookalikes” section above), emergence timing also differs, but often partially overlaps. E. dorothea is the second of the two species to hatch, typically following E. invaria by two or three weeks. Nymphs are known to crawl into the shallow stream margins, where they will swim with a slow wriggling motion to the surface, rendering emerger patterns of this species quite effective. Emergence typically occurs during the afternoon and evening hours, but can occur during cold-weather spells and during the evening during unseasonably warm weather.
Following emergence, duns are said to molt and return to the stream as spinners within a day or two. Mating and egg laying occur in the evening over riffles, and spinners often fall spent to the water at dusk. Some accounts report only the females generally falling spent to the water, but others have observed good numbers of both sexes on the water’s surface after mating and egg laying.
Massachusetts: Mid June into and through July (even August on some waters), depending on weather and water temperatures.
Degree of difficulty 15
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.
Ephemerella dorothea
Taxonmoic level
Taxonomic Name
Feature
Degree of difficulty
Order
Ephemeroptera
Wing Shape
1
Family
Ephemerellidae
3 tails.
3
Genus
Ephemerella
several sp. of Serratella that are look-alikes
3
Species
dorothea
5-8 mm, yellow to cream, 3 tails lightly barred, mid-june- July, several sp. of Serratella that are look-alikes.
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 professional.
Sources and Credits
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/9677467639/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/9118398624/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/9680703824/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/8347892312/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/8346839489/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/9240363174/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/9677458227/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/9680694298/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/9680913348/
- (c) Jerry Schoen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/79718069@N00/9118391470/
- (c) Jerry Schoen, all rights reserved, uploaded by Jerry Schoen
- (c) Stroud Water Research Center, some rights reserved (CC BY), http://www.boldsystems.org/archive/image.php?id=bold.org/272354
- Adapted by Jay Aylward from a work by (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/14552093
- Adapted by Jay Aylward from a work by (c) Jerry Schoen, some rights reserved (CC BY-SA)
- (c) Jay Aylward, some rights reserved (CC BY-SA)
