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
Once mayflies have molted into spinners, they usually gather in swarms over the river to mate. When they're done they usually fall dead, or 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. These very coordinated events are often the angler's best chance to see a good rise of trout.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:
Leptophlebia cupida (Black Quill) Mayfly Dun
View 6 PicturesThis Leptophlebia cupida dun was extremely cooperative, and it molted into a spinner for me in front of the camera. Here I have a few dun pictures and one spinner picture, and I've put the entire molting sequence in an article.
View 6 PicturesThis Leptophlebia cupida dun was extremely cooperative, and it molted into a spinner for me in front of the camera. Here I have a few dun pictures and one spinner picture, and I've put the entire molting sequence in an article.Region: Upper Midwest
Collected May 27, 2005
Added May 16, 2006
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
32 Streamside Pictures of Mayflies:
View Full Size
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).
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).
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).
Several Baetidae nymphs line up on a rock.
In this picture: Mayfly Family Baetidae (Blue-Winged Olives).
In this picture: Mayfly Family Baetidae (Blue-Winged Olives).
Recent Discussions of Ephemeroptera
does color=species? 5 Replies »
Posted by CaseyP on May 2, 2008 in the family Ephemerellidae
Last reply on May 2, 2008 by GONZO
if the "sulphurs" from one stream are peach-colored, and from another are nearly white, are they the same or different bugs? would they hatch at different times?
as a tyer, i just make them different colors, but d'you think they would hatch at around the same week or so?
ReplyPredicting a hatch?as a tyer, i just make them different colors, but d'you think they would hatch at around the same week or so?
Posted by U2ill on Apr 2, 2008
All,
Is it possible to predict a hatch (whether mayfly, caddis, stonefly, etc) based off of water, air, and weather data? So if I know streamflow, water temp, air temp, wind, cloudiness, etc...and I know what insects are on a stream...is that enough data to make a prediction like "There would be a good likelihood of a caddis hatch this afternoon"?
Replyswarm sighting along Ohio River in Pittsburgh 6 Replies »Is it possible to predict a hatch (whether mayfly, caddis, stonefly, etc) based off of water, air, and weather data? So if I know streamflow, water temp, air temp, wind, cloudiness, etc...and I know what insects are on a stream...is that enough data to make a prediction like "There would be a good likelihood of a caddis hatch this afternoon"?
I witnessed what I think was a mayfly swarm along Ohio River Blvd in Pittsburgh on Thursday, June 21st at dusk. The insects created spinning columns that were about 30-80 feet high. There were about 150-200 of these columns for about 1/2 mile along the hillside just above the sewage treatment plant, and also above a stream that feeds into the Ohio. I have been searching but can't find any documentation that the swarming behavior occurs in this column pattern. Is anyone familiar with this?
ReplyHexagenia orlando 1 Reply »Does anyone have any hatch dates for hexagenia orlando in the Central Florida area? Several lakes near me have populations and I am gathering data. I have photos and one hatch record.
ReplyTrico Tips 32 Replies »Posted by Martinlf on Jul 21, 2007 in the genus Tricorythodes
Last reply on Dec 23, 2007 by Martinlf
I'll start with a fly patterns, follow with a bit of what I think I know about Tricos (Entomologists, please offer corrections if needed), and close with a few questions.
I love designing different patterns for Tricos, partly to keep myself entertained, and partly to show the fish something new from time to time. Jason's photos and the opinions of some fussy fish have led me to tie an extra large thorax recently on all my Tricos. My old standby is a parachute tied reverse, with a high vis post over the bend of the hook, and grizzly hackle, with no tails. It's modeled on Al's Trico, which can be found on the Little Lehigh Flyshop website. It's very visible and fish generally approve. My newest fly is a take off from one of Gonzo's (Lloyd Gonzales) patterns in his book Fly-fishing Pressured Water, and it also shows the influence of Al's Trico. Gonzo ties an upside down Trico on a wide gap hook using synthetic material for the wing. I tie this fly also, and it certainly does catch fish, but I recently tied a version with grizzly hackle, making an oversize thorax and palmering hackle over the thorax to create a full wing. I then clipped hackle from the top of the fly (which becomes the bottom, as this is an upside down fly) so that the fly would sit flat, upside down, on my tying table. A drop of Locktite brush-on super glue on the bare recently clipped thorax after darkening the hackle stem with black marker and the fly was done. (By the way, I put tails on this one to balance it.) It caught several fish the first time I tried it on a heavily fished stream.
I believe for some, if not most species of Tricos, males hatch at night, females in the morning, and that the spinners fall when the air temperature hits the upper 60's. This generally means that as the season goes on, spinners hit the water later and later. Sometimes by 7:00 am (or earlier) in the early summer, by 10:00 (or later) in the fall.
It's been unseasonably cool in the Northeast the past couple of days, and I would have gone out this morning but for taking my daughter to a midnight showing of The Order of the Phoenix (I just couldn't get up) but I'm wondering if the spinner fall happens later than normal on cool mid-summer mornings like today's. I hope to find out Monday, but am curious if anyone has experiences to share. Also, does anyone have an effective Trico pattern to share? I'm always looking for ideas.
ReplyI love designing different patterns for Tricos, partly to keep myself entertained, and partly to show the fish something new from time to time. Jason's photos and the opinions of some fussy fish have led me to tie an extra large thorax recently on all my Tricos. My old standby is a parachute tied reverse, with a high vis post over the bend of the hook, and grizzly hackle, with no tails. It's modeled on Al's Trico, which can be found on the Little Lehigh Flyshop website. It's very visible and fish generally approve. My newest fly is a take off from one of Gonzo's (Lloyd Gonzales) patterns in his book Fly-fishing Pressured Water, and it also shows the influence of Al's Trico. Gonzo ties an upside down Trico on a wide gap hook using synthetic material for the wing. I tie this fly also, and it certainly does catch fish, but I recently tied a version with grizzly hackle, making an oversize thorax and palmering hackle over the thorax to create a full wing. I then clipped hackle from the top of the fly (which becomes the bottom, as this is an upside down fly) so that the fly would sit flat, upside down, on my tying table. A drop of Locktite brush-on super glue on the bare recently clipped thorax after darkening the hackle stem with black marker and the fly was done. (By the way, I put tails on this one to balance it.) It caught several fish the first time I tried it on a heavily fished stream.
I believe for some, if not most species of Tricos, males hatch at night, females in the morning, and that the spinners fall when the air temperature hits the upper 60's. This generally means that as the season goes on, spinners hit the water later and later. Sometimes by 7:00 am (or earlier) in the early summer, by 10:00 (or later) in the fall.
It's been unseasonably cool in the Northeast the past couple of days, and I would have gone out this morning but for taking my daughter to a midnight showing of The Order of the Phoenix (I just couldn't get up) but I'm wondering if the spinner fall happens later than normal on cool mid-summer mornings like today's. I hope to find out Monday, but am curious if anyone has experiences to share. Also, does anyone have an effective Trico pattern to share? I'm always looking for ideas.
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