Mayfly Species Ephemerella dorothea (Sulphur)
Taxonomic Navigation -?-
Kingdom Animalia (Animals)
» Phylum Arthropoda (Arthropods)
» Class Insecta (Insects)
» Order Ephemeroptera (Mayflies)
» Family Ephemerellidae (Hendricksons, Sulphurs, PMDs, BWOs)
» Genus Ephemerella (Hendricksons, Sulphurs, PMDs)
» Species dorothea (Sulphur)
Common Names
Ephemerella dorothea consists of two distinct subspecies (Subspecies: Entomologists sometimes further divide a species into distinct groups called subspecies, which have two lower-case words on the end of their scientific name instead of one. The latter is the sub-species name. For example, Maccaffertium mexicanum mexicanum and Maccaffertium mexicanum integrum are two different subspecies of Maccaffertium mexicanum.) which both produce excellent action. Ephemerella dorothea dorothea is a small species of Sulphur in the East, and Ephemerella dorothea infrequens (formerly Ephemerella infrequens) is one of the two main Pale Morning Dun hatches of the West.
Where & When
Regions: East, Midwest, West
Time Of Year (?): East: May-July, best in June. West: June-October, best in July-August.
Preferred Waters: Any streams, but especially good in alkaline (Alkaline: Having a pH higher than 7 (opposite of acidic). Moderately alkaline water is ideal for trout because it's better for the growth of phytoplankton, the usual base of the aquatic food chain, and that's good for the growth of everything higher up the chain, including trout.) spring creeks.
The Eastern subspecies (Subspecies: Entomologists sometimes further divide a species into distinct groups called subspecies, which have two lower-case words on the end of their scientific name instead of one. The latter is the sub-species name. For example, Maccaffertium mexicanum mexicanum and Maccaffertium mexicanum integrum are two different subspecies of Maccaffertium mexicanum.) begins to emerge in mid-late May in Pennsylvania. It progresses through the Catskills in early June and peaks in mid-June farther north, lasting as late as early July in some places.Time Of Year (?): East: May-July, best in June. West: June-October, best in July-August.
Preferred Waters: Any streams, but especially good in alkaline (Alkaline: Having a pH higher than 7 (opposite of acidic). Moderately alkaline water is ideal for trout because it's better for the growth of phytoplankton, the usual base of the aquatic food chain, and that's good for the growth of everything higher up the chain, including trout.) spring creeks.
The Western subspecies (Subspecies: Entomologists sometimes further divide a species into distinct groups called subspecies, which have two lower-case words on the end of their scientific name instead of one. The latter is the sub-species name. For example, Maccaffertium mexicanum mexicanum and Maccaffertium mexicanum integrum are two different subspecies of Maccaffertium mexicanum.) is more difficult to predict because of the higher local variation in climate. Hatches generally occur in July or August, but Caucci and Nastasi note in Hatches II that they can extend into October on stable spring creeks. Despite the wide range of emergence dates, this hatch is usually prevalent on a given stretch of water for less than a week. Fred Arbona writes in Mayflies, the Angler, and the Trout that they may appear during the last few weeks of June. Knopp and Cormier report their hatches during May in California.
Hatching Behavior
Time Of Day (?): Flexible, but typically mid-late evening in the East and Midwest, near noon in the West
Habitat: Slow water
Water Temperature: East: 60-65°F, West: 55-60°F
These insects are actually too perfect for dry fly fishing, which makes matching their hatches difficult.Habitat: Slow water
Water Temperature: East: 60-65°F, West: 55-60°F
The nymphs may drift for a while just below the surface before trying to break through. When they do, it takes them a long time to crawl out of their shucks (
View Full Size
Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.
These Sulphurs emerge from smooth, slow water, which allows the trout maximum time to inspect their prey. Because a rising trout may be selective to either floating nymphs, emergers, duns, cripples (Cripple: In fly fishing, a cripple is any insect which has been injured or deformed so that it cannot escape the water. This may include stillborn emergers or fully emerged adults which have been damaged, often by wind or waves, so that they can no longer fly. Trout often favor eating crippled insects.), or spinners, this is one of the most puzzling hatches in all fly fishing. It is also difficult because the flies are small, hook size 16 to 18, and such small imitations are prone to microdrag (Microdrag: The imperceptibly small unnatural motions of an artificial fly on the water, caused by its connection to the line. A trout's whole life is spent watching things drift naturally, and unnatural movement too subtle for us to detect is obvious to their specialized senses.). There is no better time to hone your powers of observation and presentation.
Spinner Behavior
Time Of Day: Near dusk in the East; usually morning and often again near dusk in the West
Habitat: Riffles are preferred, but on spring creeks without riffles any broken water will do.
Hatched duns typically return to the stream within two days as spinners. After mating, both genders fall spent (Spent: The wing position of many aquatic insects when they fall on the water after mating. The wings of both sides lay flat on the water. The word may be used to describe insects with their wings in that position, as well as the position itself.) on the water.Habitat: Riffles are preferred, but on spring creeks without riffles any broken water will do.
Females usually, but not always, drop their eggs from the air above the stream. When they do end up on the water with egg sacs still attached, trout may become selective to spinners with little bright green dots near the tail. Patterns are sold to imitate this. Knopp & Cormier say trout are often selective to one gender or the other when the Western subspecies (Subspecies: Entomologists sometimes further divide a species into distinct groups called subspecies, which have two lower-case words on the end of their scientific name instead of one. The latter is the sub-species name. For example, Maccaffertium mexicanum mexicanum and Maccaffertium mexicanum integrum are two different subspecies of Maccaffertium mexicanum.) falls, and I suspect the egg sacs are the main difference between the two.
Nymph Biology
Current Speed: Some in riffles and runs, but best in slow streams and pools, especially near vegetation.
Substrate: Gravel, sand, vegetation
The nymphs display the usual Ephemerellidae habits of high activity in the hours and days before they hatch, and trout claim many of them before they're anywhere near the surface.Substrate: Gravel, sand, vegetation
Ephemerella dorothea Fly Fishing Tips
See the section on Hatching Behavior above regarding the many challenges this hatch poses. The best approach is extremely keen observation, and the standby is rapid-fire trial and error. Do not stick with one thing for very long if it's not working.Caucci and Nastasi note in Hatches II that some light-bodied species of Epeorus, such as Epeorus vitreus, may emerge at the same time as dorothea in the East. It's just one more entry in the long list of complications of the dorothea Sulphurs.
2 Mayfly Specimens in the Species Ephemerella dorothea:
Ephemerella dorothea (Sulphur) Mayfly Nymph
View 6 PicturesI keyed this nymph carefully under a microscope to check that it's Ephemerella dorothea.
View 6 PicturesI keyed this nymph carefully under a microscope to check that it's Ephemerella dorothea.Region: Poconos
Collected May 29, 2007
Added Jun 4, 2007
Ephemerella dorothea (Sulphur) Mayfly Dun
View 5 Pictures
View 5 PicturesRegion: Poconos
Collected May 27, 2007
Added Jun 4, 2007
Recent Discussions of Ephemerella dorothea
Wow, they really can take forever to get off the water 36 Replies »
I watched quite a few of these guys emerge tonight. (I think -- they seemed too small and light to be Ephemerella invaria, though I didn't bring one home to check under the microscope.) It was a cool evening but not cold, and they were emerging on the slow flats of a large midwestern spring creek. I watched several of them drift 50+ feet on the very slow-moving water, slowly rising up out of the surface film. Their emergence was sporadic and lucky for them the trout were also sporadic. Many were eaten but others went ignored for their entire lengthy drifts.
Later in the evening I was bested by a half-dozen rising trout. The sulphurs were still emerging, and a mix of spinners was starting to appear on the water, but I didn't get so much as a splashy refusal from several rising fish, even in the low light of dusk. My best guess is that they were picky feeders keying on a stage of Ephemerella dorothea mayflies.
ReplyLater in the evening I was bested by a half-dozen rising trout. The sulphurs were still emerging, and a mix of spinners was starting to appear on the water, but I didn't get so much as a splashy refusal from several rising fish, even in the low light of dusk. My best guess is that they were picky feeders keying on a stage of Ephemerella dorothea mayflies.
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