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**Mayfly Genus Siphlonurus (Gray Drakes)**

Mayflies

Caddisflies

Stoneflies

Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Siphlonuridae (Gray Drakes)

» Genus Siphlonurus (Gray Drakes)

Species in Siphlonurus
Siphlonurus alternatusGray Drake	0	0
Siphlonurus autumnalisGray Drake	0	0
Siphlonurus columbianusGray Drake	0	0
Siphlonurus occidentalisGray Drake	0	0
Siphlonurus phyllisGray Drake	0	0
Siphlonurus quebecensisGray Drake	0	0
Siphlonurus rapidusGray Drake	0	0
Siphlonurus spectabilisGray Drake	0	0

12 species aren't included.

Common Names

Match	Common Name
	Gray Drakes
	Black Drakes

Pictures Below ↓

The important Eastern species are Siphlonurus quebecensis, Siphlonurus alternatus, and to a lesser extent Siphlonurus rapidus. All may produce fishable spinner falls, often with more than one species in the same swarm, but these are generally localized and minor events compared to the classic superhatches.

The main Western species, Siphlonurus occidentalis, is much more valuable. Its importance in the West is often compared to that of Isonychia in the East.

Where & When

Preferred Waters: Slow, 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.) streams and lakes

Siphlonurus hatches are generally slow-paced events, and it takes two to three months for the entire generation to hatch out of a given stretch of water. See the species pages for emergence details about each one.

Hatching Behavior

Time Of Day (?): Morning through midday

Habitat: Slow, shallow water

Water Temperature: Varies, but 60-63°F is ideal

There is some disagreement about exactly how Siphlonurus duns hatch. It is certain that they crawl out onto shore sometimes and hatch on the surface at other times, but which of these behaviors is more prominent is anybody's guess.

The time of emergence is also up in the air; most say it is in the morning, but there are reports of emergence in the afternoon and in the middle of the night, as well. One account suggests it is most common in the evening.

Authors generally agree that, regardless of hatching mode or time, the duns are the least important stage of this species. There are reports of trout feeding well on them, and this is sometimes attributed to the wind blowing the duns into the water.

In Mayflies Ted Fauceglia relays a detailed account by Dick Stewart of the hatching of Siphlonurus duns, quoted here in part:

They then emerge by swimming toward the surface and immediately taking flight. They pop through the surface film like miniature helicopters rising toward the open sky. We believe that molting takes place either very quickly or when the duns are high in the trees, for try as we might, we almost never can find a dun (day or night) despite the fact that we can locate hundreds of spinners.

Another point on which most agree is that Siphlonurus duns emerge from very shallow margins and backwaters, sometimes far from the trout in the main channel.

Spinner Behavior

Time Of Day: Usually dusk in the East and Midwest, morning in the West, sometimes afternoon in cold weather

Gray drakes return as spinners two to four days after hatching as duns, and they gather in swarms over the riffles. Accounts of their ovipositing behavior vary: some say the females repeatedly dive and dip their abdomens briefly into the water, while others say they drop their eggs from the air. Both genders eventually 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.), but the spinner falls may be tricky to locate because the females sometimes fly far upstream after mating but before ovipositing. Trout may feed on Siphlonurus spinners very selectively.

Nymph Biology

Current Speed: Slow

Substrate: Silt, vegetation

Siphlonurus nymphs are not completely intolerant of medium to fast current, but their best populations are found in slow streams or still waters, often with plenty of weed growth. They are more frequently important to fly fishers than the duns.

They are extremely adept swimmers.

Pictures of 22 Mayfly Specimens in the Genus Siphlonurus:

Specimen Page:12 3

Siphlonurus quebecensis (Gray Drake) Mayfly Nymph

View 9 Pictures

Collected May 13, 2007 from the Delaware River in New York
Added to Troutnut.com by Troutnut on May 18, 2007

Male Siphlonurus quebecensis (Gray Drake) Mayfly Spinner

View 10 Pictures

Collected June 2, 2005 from the Namekagon River in Wisconsin
Added to Troutnut.com by Troutnut on May 24, 2006

Siphlonurus quebecensis (Gray Drake) Mayfly Nymph

View 5 PicturesI photographed this nymph in the middle of molting between one instar (Instar: Many invertebrates molt through dozens of progressively larger and better-developed stages as they grow. Each of these stages is known as an instar. Hard-bodied nymphs typically molt through more instars than soft-bodied larvae.) and the next (not hatching).

Collected May 13, 2007 from the Delaware River in New York
Added to Troutnut.com by Troutnut on May 18, 2007

Specimen Page:12 3

3 Underwater Pictures of Siphlonurus Mayflies:

View Full Size and Comment (2X larger)

In this picture: Mayfly Genus Siphlonurus (Gray Drakes).

StateNew York

LocationWest Branch of the Delaware River

Date TakenMay 13, 2007

Date AddedJun 5, 2007

AuthorTroutnut

CameraPENTAX Optio WPi

View Full Size and Comment (2.2X larger)

Several fast-swimming Siphlonurus nymphs blend in very well with the silt in this slow backwater along a trout stream.

In this picture: Mayfly Genus Siphlonurus (Gray Drakes).

StateWisconsin

LocationNamekagon River

Date TakenMay 15, 2004

Date AddedJan 25, 2006

AuthorTroutnut

CameraOlympus C740UZ

View Full Size and Comment (1.9X larger)

In this picture: Mayfly Genus Siphlonurus (Gray Drakes).

StateWisconsin

LocationNamekagon River

Date TakenMay 15, 2004

Date AddedJan 25, 2006

AuthorTroutnut

CameraOlympus C740UZ

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Jargon Defined:

Abdomens: The rear and usually the longest (ten-segmented in mayflies) portion of an insect's body, to which the tails are attached.

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.

Duns: Mayflies have two adult stages. They first emerge from the water as duns (scientifically known as the subimago stage). They then molt into the spinner (imago) stage, in which they mate and die. Sometimes the word "dun" is confusingly used to refer to a brownish gray color in fly tying materials.

Emergence: The transformation of a nymph or pupa into the adult winged stage of an insect. The term may refer to the emergence of an individual, or the daily or yearly event in which all individuals of a species emerge.

Instar: Many invertebrates molt through dozens of progressively larger and better-developed stages as they grow. Each of these stages is known as an instar. Hard-bodied nymphs typically molt through more instars than soft-bodied larvae.

Molting: When aquatic insects with hard exoskeletons (like mayfly and stonefly nymphs) grow bigger, their exoskeleton does not grow with them. Instead they grow a new, larger one underneath and shed the old one when it's too small. This process is called molting.

Nymphs: The juvenile, underwater stages of mayflies, stoneflies, dragonflies, and damselflies and other aquatic insects whose juvenile stages are covered by hard exoskeletons. The word can also refer to the fishing flies which imitate these creatures, in which case it is used as a blanket term for flies imitating any underwater stage of an invertebrate (except for crayfish and leeches).

Ovipositing: To lay eggs.

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: There are two winged stages of adult mayflies. They emerge from the water as duns, molt on land (usually) into their fully mature stage, spinners. As spinners, they mate, lay eggs, and die.

Useful References:

Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.

Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.

Fauceglia, Ted. 2005. Mayflies . Stackpole Books.

Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.

Schwiebert, Ernest G. 1955. Matching the Hatch. MacMillan Publishing Company.

Swisher, Doug and Carl Richards. 2000. Selective Trout. The Lyons Press.