Mayfly Genus Rhithrogena

Mayflies

Caddisflies

Stoneflies

Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Heptageniidae (March Browns, Cahills, Quill Gordons)

» Genus Rhithrogena

Species in Rhithrogena
Rhithrogena futilisWestern Gordon Quill	0	0
Rhithrogena hageniWestern Black Quill	0	0
Rhithrogena impersonataDark Red Quill	3	19
Rhithrogena jejunaDark Red Quill	0	0
Rhithrogena manifesta	0	0
Rhithrogena morrisoniWestern March Brown	0	0
Rhithrogena robusta	0	0
Rhithrogena undulataSmall Western Red Quill	0	0

15 species aren't included.

Pictures Below ↓

This genus is widespread across the country, but it is only really important to anglers in the West.

The East/Midwest species are Rhithrogena jejuna, Rhithrogena manifesta, and Rhithrogena impersonata, which is arguably the most important of these unimportant species. All of them are widespread and none of them are abundant except in rare locations, mostly in Michigan and Wisconsin.

Other Rhithrogena species are among the most important mayflies in the West. The best hatches come from Rhithrogena morrisoni and Rhithrogena hageni. The three species Rhithrogena undulata, Rhithrogena futilis, and Rhithrogena robusta are still probably more important than their Eastern counterparts.

Hatching Behavior

All of Rhithrogena emerge underwater. Most do so on the stream bottom and float all the way to the surface a duns, but those emerging from slow water will rise most of the way as nymphs before struggling free of their shucks (

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Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.

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.).

Nymph Biology

Rhithrogena nymphs have been portrayed strangely in angling texts, to the extent that I did not recognize them in the first samples I collected. They are best known for their unique gills: the first and last pair of gills wrap around the bottom side of the abdomen, creating a "suction cup" which helps them cling to rocks in water even faster than other clingers can tolerate.

Book illustrations make these gills look obvious and nearly opaque, probably because it's hard to draw them any other way in pencil. But this really misrepresents the actual insects; you have to look pretty closely to notice the gill extensions under the body. They are very translucent and easy to miss.

Drawings also show these nymphs with short, robust, crab-like body shapes, perhaps to somehow emphasize their proficiency as clingers. They are great clingers, but their bodies are more narrow and streamlined than drawings indicate. My photos demonstrate this.

4 Mayfly Specimens in the Genus Rhithrogena:

Specimen Page:12

Rhithrogena Mayfly Spinner

View 9 PicturesI'm very tentatively (see the connected forum thread) sticking this mayfly in Rhithrogena for now.

Region: Catskills

Collected Jun 7, 2007

Added Jun 8, 2007

Rhithrogena impersonata (Dark Red Quill) Mayfly Nymph

View 8 PicturesThis specimen shows one of two distinct color types of Rhithrogena impersonata nymphs. This type is very reddish, especially in the gills, and it was formerly in its own species called Rhithrogena sanguinea.

Region: Upper Midwest

Collected Jun 5, 2005

Added May 25, 2006

Rhithrogena impersonata (Dark Red Quill) Mayfly Nymph

View 6 PicturesThis was the only Rhithrogena specimen in a large sample of nymphs from a small Catskill stream. It looks virtually identical to Rhithrogena impersonata specimens collected in the Midwest, but I didn't get to check the distinguishing features under a microscope.

Region: Catskills

Collected Apr 19, 2006

Added Apr 21, 2006

Specimen Page:12

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Jargon Defined:

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

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.

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).

View Full Size

Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.

Shucks: 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.

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.

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

Leonard, Justin W. and Fannie A. Leonard. 1962. Mayflies of Michigan Trout Streams. Cranbrook Institute of Science.