This species, the primary "Sulphur" hatch, stirs many feelings in the angler. There is nostalgia for days when everything clicked and large, selective trout were brought to hand. There is the bewildering memory of towering clouds of spinners which promise great fishing and then vanish back into the aspens as night falls. There is frustration from the maddening selectivity with which trout approach the emerging duns--a vexing challenge that, for some of us, is the source of our excitement when Sulphur time rolls around.
» Species invaria (Sulphur Dun)
Ephemerella invaria is one of the two species frequently known as Sulphurs (the other is Ephemerella dorothea). There used to be a third, Ephemerella rotunda, but entomologists recently discovered that invaria and rotunda are a single species with an incredible range of individual variation. This variation and the similarity to the also variable dorothea make telling them apart exceptionally tricky.
As the combination of two already prolific species, this has become the most abundant of all mayfly species in Eastern and Midwestern trout streams. Where & When
Regions:The invaria hatch begins in early May in Pennsylvania. The Catskills peak in late May and early June, while mid-June is best in the Adirondacks and the northern fringe of the Upper Midwest.
East, MidwestTime Of Year (?):
Good fishing from this hatch usually lasts about two weeks in a particular location.Hatching Behavior
Time Of Day (?):Ephemerella invaria nymphs drift for some time just below the surface as they begin to emerge, and these floating nymphs cause rises to the surface which may fool the angler into thinking the trout are taking duns.
Flexible based on weather. Generally mid-afternoon at first and later as the season progresses.Habitat:
Almost anywhere, but best near fast runs and riffles.Water Temperature:
Emergence itself takes quite a while, making emerger patterns more important for this hatch than for most. This importance is heightened by the lower availability of the fully formed duns. These duns take to the air more quickly than most of their Ephemerella kin, but anglers should still be prepared to imitate them if need be.Spinner Behavior
Time Of Day: DuskDuns typically molt and return to the water as spinners within one day. The females drop their eggs in mid-air and are not exposed to trout until they 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.)--if they 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.) at all.
Knopp & Cormier write in Mayflies: An Angler's Study of Trout Water Ephemeroptera that the males seldom 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 and the females only fall sometimes. Ted Fauceglia's Mayflies says 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. This disagreement mirrors the confusion I've felt about this species on the stream; the spinners are generally unpredictable, but they can provide excellent fishing.Nymph Biology
Current Speed:These are among the most adaptable of mayflies, thriving in many types of habitat. They inhabit warmwater streams as well as cold and are found up and down the channel in riffles, pools, and runs. They are most prolific in deep, gravel-bottomed riffles.
Usually medium to fast, sometimes slowSubstrate:
Many types, but gravel is preferredEnvironmental Tolerance:
Unlike Ephemerella subvaria
is very tolerant of a wide range of conditions.
In the days and hours before the hatch these nymphs become especially active, so their imitation is especially useful. They clamber to better emergence sites where they rest in plain view of both trout and photographers (see my underwater photos). They also make apparent "practice runs" to and from the surface in the manner of Ephemerella subvaria.
The nymphs are a little bit difficult to recognize because they their base color ranges from brown to olive and they're adorned with many possible color patterns. Anglers should be prepared with imitations in brown and olive, hook sizes 12 through 16.Ephemerella invaria Fly Fishing TipsTake extra care during emergence to figure out if the trout are feeding on floating nymphs, emergers, or duns, and what size Sulphur they are taking. The invaria duns can be hook size 14 or 16. The possibility of confusing them with the smaller Ephemerella dorothea adds to the Sulphur challenge. Remember that the solution to this puzzle may vary from fish to fish, and you should switch flies or switch fish quickly if what you're trying isn't working.
Pictures of 45 Mayfly Specimens in the Species Ephemerella invaria:
2 Streamside Pictures of Ephemerella invaria Mayflies:
This Ephemerella invaria
sulphur dun got stuck in its shuck (Shuck: The shed exoskeleton left over when an insect molts into its next stage or instar. Most often it describes the last nymphal or pupal skin exited during emergence into a winged adult.)
trying to emerge. This isn't exactly a "natural" pose for a photograph, but it kind of
shows what an emerger pattern could look like.In this picture: Mayfly Species Ephemerella invaria (Sulphur Dun).
Date AddedJun 5, 2007
CameraPENTAX Optio WPi
Date AddedJun 5, 2007
CameraPENTAX Optio WPi
15 Underwater Pictures of Ephemerella invaria Mayflies:
Underwater Photo Page:123 Underwater Photo Page:123
Recent Discussions of Ephemerella invaria
Aw Shucks 10 Replies »
OK, this is going to seem like a major duh experience for some of you, but the other night I found a sulphur spinner on the door of a bathhouse in a campground I was staying at. Looking for other bugs I then saw a pale nymph shuck on the door. I was totally confused. A nymph this far from the stream? Was this some alien bug? Looking closer I noticed that the shape was too slender for a nymph and that the wing pads were more like little protruding pockets--and it hit me. Spinner shuck. I knew that mayflies molted to produce a spinner, but I had thought the shuck would be more insubstantial--something that would be flimsy and lack form. This was so cool, and at the same time I felt so silly for thinking it could somehow have been a nymph shuck. It's the first spinner shuck I've seen, but I assume that I'll start seeing them everywhere now, like a new word you learn. Anybody else have a spinner shuck story?ReplyHatching Sulphur
Click on "40 more specimens" and scroll down for one photo.Reply
Your Thoughts On Ephemerella invaria:
You must log in
at the top of the page to post. If you haven't registered yet, it's this easy: