Insect Order Ephemeroptera (Mayflies)
Taxonomic Navigation -?-
Kingdom Animalia (Animals)
» Phylum Arthropoda (Arthropods)
» Class Insecta (Insects)
» Order Ephemeroptera (Mayflies)
8 families aren't included.
Common Name
| Match | Common Name |
 | Mayflies |
Fly Imitations by Orvis
| Stage | Fly Pattern |
| Nymph | Hare's Ear |
| Nymph | Pheasant Tail |
| Nymph | RS2 |
| Dun | Adams |
| Dun | CDC Comparadun |
| Dun | Sparkle Dun |
| Spinner | AK's Spinner |
Hatching Behavior
Mayflies live as nymphs for 3 months to 2 years, depending on the species. When they're mature, the entire generation emerges from the stream as adults, often within the span of a couple weeks. They emerge as "duns," an immature winged adult stage, and molt within a day or two into "spinners," the mature adults, which I discuss below.The duns most often emerge during an hour or two each day for a couple weeks sometime in the spring or summer, though there's great variation between species. These events are barely noticeable in some species and reach nightmarish proportions in others.
There are three ways mayfly nymphs emerge into duns. Most often, the nymph swims to the water's surface and splits open its exoskeleton above the thorax (Thorax: The thorax is the middle part of an insect's body, in between the abdomen and the head, and to which the legs and wings are attached.). The dun wriggles out onto the surface, and many species float along on the surface for a while as their wings dry. These species make prime targets for hungry trout, and they are the dry fly fisherman's favorites. But many important species don't follow this pattern, and anglers benefit from knowing when to match a different style of emergence.
In a some species, the winged dun emerges from its nymphal case several feet underwater and swims to the surface, wings and all. Old-style winged wet flies match these hatches, but newer sparkle yarn patterns work better. Other species emerge by crawling out onto streamside rocks or logs as nymphs. The adults emerge there on land, so they offer little to the angler unless there's enough wind to blow them back into the water. Most writers suggest matching the migrating nymphs when these hatches are underway.
Spinner Behavior
Mayfly females face the extra duty of laying their eggs after mating. Many species release their eggs as 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.) on the water. Some land on the water, release a few, and take off again. Others fly low over the water and tip the tips of their abdomens below the surface for just a moment to release eggs. Other species drop their eggs from high in the air. In one very common genus, Baetis, the females land near shore and crawl underwater to lay their eggs in neat little rows on rocks and logs.
Like most things in nature, mayfly spinners aren't as predictable as we'd like. Sometimes clouds of thousands of spinners will gather over a riffle in the evening and fly back into the woods as quickly as they came, never falling 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.).
Spinner falls can happen at any time of day, depending on species, but dusk is by far the most common time. These events are usually much more concentrated than the dun emergence of the same species, which means that many species which are unimportant as duns due to sporadic emergence become very important as spinners.
Some spinner falls take place over every type of water, but most species choose riffles.
Anglers imitating spinners can learn much by carefully watching the real things drifting on the water. Their silhouette and posture does not match the shape of "traditional" spinner patterns; they're more accurately imitated by innovative fly patterns like the Ellis Triple Wing and Galloup's Crippled Spinner described in Kelly Galloup's outstanding book, Cripples & Spinners.
Nymph Biology
Anglers recognize four categories of mayfly nymphs: swimming, burrowing, clinging, and crawling:- Some streamlined swimmers move like little bullets, faster then fish of the same size, and they swim upstream against strong current without a problem. Others inhabit slow water and use their speed to dart between leaves in the weed beds.
- Clingers of the family Heptageniidae are typically flat nymphs with strong legs and claws for holding on to rocks in very fast water. Some have evolved further adaptations for clinging; for example, the genus Rhithrogena has suction-cup-like gills. There is great variation among the clingers and some species have adapted to slow water.
- Crawlers come in the most varied forms; they are a catch-all group for "average" families which excel at neither swimming nor clinging. The Hendricksons and Sulphurs of the Ephemerella genus are typical crawlers. There are tiny crawlers like Tricorythodes, and there are oddballs like Baetisca. The crawlers in Leptophlebiidae are quite good at swimming, and those in Drunella are quite good at clinging.
- The distinctive burrowers of Ephemeridae (and the less important Polymitarcyidae) are pale nocturnal creatures which use tusks to carve U-shaped burrows into the river bottom, where they live most of the time. Their long yellow bodies and feathery gray gills make them unmistakable. Their hatches are some of the angler's favorites, especially the giant Hexagenia limbata flies of the Midwest and the Eastern Green Drakes, Ephemera guttulata.
Entomologists have a similar system, but even their line between categories is a blurry one. Some burrowers swim well, some crawlers cling well, and some families, like Potamanthidae, straddle the boundary between categories.
If you fish a fertile stream, watch the bottom ahead of you as you walk. Sometimes, especially in April and May, you'll see lots of mayfly nymphs in front of you swimming out of your way or scurrying to the undersides of rocks. You don't need to be down on all fours with a magnifying glass to see mayfly life underwater.
516 Mayfly Specimens:
Hexagenia atrocaudata (Late Hex) Mayfly Spinner
View 12 Pictures
View 12 PicturesRegion: Upper Midwest
Collected Jul 24, 2005
Added Apr 15, 2006
Hexagenia limbata (Hex) Mayfly Spinner
View 13 Pictures
View 13 PicturesRegion: Upper Midwest
Collected Jun 26, 2005
Added May 26, 2006
Isonychia bicolor (Mahogany Dun) Mayfly Spinner
View 15 PicturesI got several really nice pictures of this spinner. I also collected a female on the same trip.
View 15 PicturesI got several really nice pictures of this spinner. I also collected a female on the same trip.Region: Northeast
Collected Aug 9, 2006
Added Aug 11, 2006
32 Streamside Pictures of Mayflies:
View Full Size
A thick mating swarm of Tricorythodes mayfly spinners hovers over a cool Catskill tailwater one early fall morning. View the picture full-size and you'll be able to make out the wings and tails on most of those little white dots.
This was one of many such clouds visible all up and down the river. The mayflies were impressive, but the trout did not hold up their end of the bargain -- there was not a rise in sight.
In this picture: Mayfly Genus Tricorythodes (Tricos).
This was one of many such clouds visible all up and down the river. The mayflies were impressive, but the trout did not hold up their end of the bargain -- there was not a rise in sight.
In this picture: Mayfly Genus Tricorythodes (Tricos).
Often mayflies can be found on houses near the river. This one molted from a dun into a spinner on the outside of our kitchen window.
Any lit dwelling near the river can attract a lot of mayflies at night. A good way to determine what's hatching is to visit a gas station (or anything else with bright lights) close to the river early in the morning.
In this picture: Mayfly Family Baetidae (Blue-Winged Olives).
Any lit dwelling near the river can attract a lot of mayflies at night. A good way to determine what's hatching is to visit a gas station (or anything else with bright lights) close to the river early in the morning.
In this picture: Mayfly Family Baetidae (Blue-Winged Olives).
This Epeorus pleuralis nymph tried to hatch into a dun while attached to this rock and apparently got stuck. This species is supposed to emerge from its nymphal 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.) on the bottom of the stream and swim to the surface as a bedraggled dun. It seems more like this one was trying to crawl out onto a rock to emerge. The rock itself is covered with a thin layer of fast water in a riffle, and apparently it prevented the dun from making any headway. You can see the dun's eyes and a bit of the mesonotum (Mesonotum: The top of the insect mesothorax.) if you look closely.
In this picture: Mayfly Species Epeorus pleuralis (Quill Gordon).
View Full SizeHere's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.
In this picture: Mayfly Species Epeorus pleuralis (Quill Gordon).
67 Underwater Pictures of Mayflies:
This is my favorite underwater picture so far. It shows a bunch of Simuliidae (black fly) larvae clinging to a rock and swinging in the fast current. There are also at least four visible mayfly nymphs, probably in the family Baetidae.
In this picture: Mayfly Family Baetidae (Blue-Winged Olives) and True Fly Family Simuliidae (Black Flies).
In this picture: Mayfly Family Baetidae (Blue-Winged Olives) and True Fly Family Simuliidae (Black Flies).
This Ephemerella subvaria (Hendrickson) nymph picture is one of my favorites.
In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
A crayfish chews on a Hexagenia limbata nymph shortly after a small Hex emergence. I didn't catch any fish, but playing around with my flashlight and camera in the rocks proved productive.
In this picture: Arthropod Order Decapoda (Crayfish) and Mayfly Species Hexagenia limbata (Hex).
In this picture: Arthropod Order Decapoda (Crayfish) and Mayfly Species Hexagenia limbata (Hex).
Recent Discussions of Ephemeroptera
Learning to Use the Force 6 Replies »
Posted by Martinlf on Jun 18, 2009 in the genus Serratella
Last reply on Jun 23, 2009 by Martinlf
Went over to the Dark Side the past two days. Thanks to all who helped. By the way, Jason, fished spinners also.
ReplyEmerger 6 Replies »Posted by Martinlf on Jun 10, 2009 in the genus Serratella
Last reply on Jun 12, 2009 by GONZO
Does anyone know the color of the emerging/freshly emerged dun?
ReplyS. basale on Clarks Creek, PA 1 Reply »Posted by Wiconisco37 on Feb 4, 2009 in the species Siphloplecton basale
Last reply on Jun 10, 2009 by Martinlf
they were discovered on Clarks Creek by a man from halifax, PA
i dont know what their numbers were like thgough
ReplyAw Shucks 7 Replies »i dont know what their numbers were like thgough
Posted by Martinlf on May 19, 2009 in the species Ephemerella invaria
Last reply on May 21, 2009 by Wiflyfisher
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?
ReplyParalep Hatching Behavior 9 Replies »Posted by Shawnny3 on Apr 6, 2009 in the genus Paraleptophlebia
Last reply on Apr 30, 2009 by Taxon
I can't remember where I read or heard these things (might have been on this site), but I want to make sure my vague recollections are not totally false. When Paraleptophlebia are mating, do they make exaggerated dives in clouds above the stream? If so, do they often end up in the water at these times or do they fall as spinners much later? Finally, when they emerge, do they do so at the stream bottom and then swim to the surface as duns?
Thanks for any help,
Shawn
ReplyThanks for any help,
Shawn
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