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

Taxonomic Navigation -?-
» Family Heptageniidae (March Browns, Cahills, Quill Gordons)
Genus in HeptageniidaeNumber of SpecimensNumber of Pictures
CinygmaWestern Light Cahills00
CinygmulaDark Red Quills00
EcdyonurusWestern Ginger Quills00
EpeorusLittle Maryatts09
MaccaffertiumMarch Browns and Cahills01
StenacronLight Cahills00

4 genera aren't included.
Common Name
Pictures Below
Known as the "clinger" mayflies to anglers, a few species of this family can be extremely prolific, with a lot more that aren't. These lesser species account for many of the curious mayflies you find that never seem to associate with a major hatch, let alone a fishable one. Not all heptageniid species are so scarce though; there are superhatches too.

Heptageniids can be broken into "groups" of similar genera (based on angling concerns) to help keep track of them. Although many of them are closely related, they are not officially divided in this way by entomologists. Here are the groups:

Former Stenonema (blotchy wings)

The genus Stenonema, who's Latin name was one of the first etched in the minds of anglers has now been relegated to the minor leagues containing only one species of importance Stenonema femoratum, one of several Lt. Cahills. Its former species of angling legend are now split between the newer genera Maccaffertium and Stenacron. These include the March Brown (prev. S. vicarium) and Gray Fox (prev. S. fuscum) superhatches, further condensed into the one species Maccaffertium vicarium.
The current and former Stenonema species are for all practical purposes limited to the East and Midwest.

Former Heptagenia (plain wings)

While Heptagenia has held on to more species than Stenonema, many of its fishable hatches have been moved to the new genera Leucrocuta, Nixe, and Ecdyonurus. There are many former Heptagenia species across the continent, but few are important to anglers and of those, more are in the West than in the East.

Epeorus (two-tailed Nymphs, plain wings)

The closely related genera Epeorus and Ironodes are among the only mayflies to have just two tails as nymphs. Good populations can be found in the West, but it's in the East where the mayfly named after the man that brought the dry fly to America can be found, the superhatch Epeorus pleuralis or Quill Gordon.

Rhithrogena (suction cup gills)

The genus Rhithrogena can be identified by the gills of its nymphs. They extend underneath the abdomen in the front and the back. They are very important for early season anglers in the West, but not very often in the East. For western anglers, it's duns are the blotchy winged equivalent of the East's March Brown (Maccaffertium vicarium). Ironically, it is only the Western March Brown that is in the same genus as the English species for which the common name originated.

Cinygmula (horn heads)

The genus Cinygmula is easily distinguished by the nymph's enlarged palpi (mouth parts) that stick out from both sides of their heads like little blunt horns. They rarely produce fishable hatches, and none are of much significance except for a few species, mostly in certain locales of the West.

Hatching Behavior

Time Of Day (?): Usually midday moving towards evening as the season progresses

Habitat: Fast water rapids and riffles over stony substrata; The margins also during emergence cycle

Many heptageniid mayflies emerge from their nymphal shucks (
Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.
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.
on the stream bottom or during their rise to the surface. Others hatch in the surface film. Others still migrate to the shallow margins and use any of the three ways. All of this may depend on habitat and current conditions as much as differences between species. Read about the species you need to match for more details, but there is no substitute for astute observation streamside.

Nymph Biology

The Heptageniidae family contains the angler's "clinger" type mayfly nymphs commonly referred to as "Flat Heads" by entomologists. They sport flattened profiles, blunted broad heads, and stout legs suitable for life in fast water. Their flattened tear drop shape is a "miracle" of nature's hydrodynamic engineering employing the same principles used by Formula One race cars to hug the road and reduce wind resistance.

Pictures of 215 Mayfly Specimens in the Family Heptageniidae:

Specimen Page:1234...23
Male Stenacron (Light Cahills) Mayfly DunMale Stenacron (Light Cahills) Mayfly Dun View 13 Pictures
Collected May 27, 2005 from the Teal River in Wisconsin
Added to by Troutnut on May 22, 2006
Specimen Page:1234...23

11 Underwater Pictures of Heptageniidae Mayflies:

Underwater Photo Page:12
In this picture: Mayfly Genus Epeorus (Little Maryatts) and Mayfly Family Baetidae (Blue-Winged Olives). From Mongaup Creek in New York.
Date TakenApr 19, 2006
Date AddedApr 22, 2006
CameraPENTAX Optio WPi
In this picture: Mayfly Genus Epeorus (Little Maryatts) and Mayfly Family Baetidae (Blue-Winged Olives). From Mongaup Creek in New York.
Date TakenApr 19, 2006
Date AddedApr 22, 2006
CameraPENTAX Optio WPi
Underwater Photo Page:12

Recent Discussions of Heptageniidae

Clinger nymphs are shaped that way to hang in really fast currents. Really? 14 Replies »
Posted by Entoman on Feb 24, 2013 in the genus Rhithrogena
Last reply on Jun 14, 2017 by Steamntrout
It is commonly held that clingers are flattened to make their lives better adapted to faster water. Their teardrop shape is certainly a classic symbol of aero and hydrodynamic perfection, so there must be some connection, right? It seems to me that such ideas show a complete misunderstanding of the hydraulic reality in which they live. Current is negligable even in the fastest a few mm. from the surface of solid objects. In fact, it is actually quite calm. I've observed baetids clinging by their tippy toes to the tops of rocks in fast riffles with no apparent effort, often next to clinger species that look like they're hanging on for dear life. What if clinger nymphs are flattened not to hold their place in fast currents but rather to facilitate movement in their ecological niche of the cramped spaces under and between cobble or crevices in other substrate types?

It is also thought that the gills of some species form ''suction'' to hold them in place. Since suction is a phenomena of vacuum creation in the atmosphere, how are these nymphs accomplishing this underwater? Is it their ultra delicate gills that hold them in place or a firm claw grip? The horizontal sprawl of the legs masks this as the gills stay in place until the legs brake free. Exposed to the air, the gills seem to laminate against the rock, just as crepe paper would if first held underwater before a rock was lifted out into the air from underneath it. However, underwater their gills behave like the crepe, flowing freely. They are performing their function as gills not suction cups. I find it hard to believe they evolved the way some think merely so they can make it more difficult for humans to pluck them from rocks in the atmosphere. How is it these mighty structures that defy our attempts to pry them from the rocks curiously fall off so easily when prodded for inspection a few seconds later in a tray or jostled in a container on the way home?

Even many scientific papers have encouraged these dubious beliefs so it's not just angler myth... And they go unchallenged... Thoughts?
ReplyM. ithaca in M. mediopunctatum section? 3 Replies »
Posted by GONZO on Sep 1, 2012 in the species Maccaffertium mediopunctatum
Last reply on Sep 4, 2012 by Entoman
Hi Jason,

In this section, the Midwestern nymphs (#573 & #574) with the dark irregular ventral bars across the anterior portion of the sternites look like Maccaffertium mediopunctatum arwini (the Midwestern ssp.), but the two Eastern duns (#733 & #765) and the associated shuck (of #765) and nymph (#764) look more like Maccaffertium ithaca to me.

Three Maccaffertium species can have very similar ventral markings in the nymph—dark, sinuate, chevron-shaped bars on many of the sternites and dark lateral marks (sometimes connected to form an inverted U-shaped mark) on segment 9. The Eastern mediopunctatum subspecies, M. m. mediopunctatum, has these markings, as does M. ithaca. Similar markings also appear as a less-common variant marking of M. modestum (or the M. modestum species complex). However, these species differ in the length and location of posterolateral projections, leg markings, the appearance of the subs and adults, and size.

Although interpretation of posterolateral projections can be tricky, those projections should help to separate the nymph (and husk) from mediopunctatum. On mediopunctatum, projections are usually on segments 3-9, 4-9, or 5-9, and those on 8 and 9 are fairly long. On ithaca, projections are usually on segments 6-9 or 7-9, and those on 8 and 9 are somewhat shorter (when compared to mediopunctatum). The twin brown bands on the femora of the nymphs should also help to separate them from modestum and mediopunctatum (usually three or four in those species).

The brown posterior margins and median dorsal stripes of the duns (similar to those found in M. vicarium) are typical of ithaca. In McDunnough’s original description of mediopunctatum (1926), he mentions that some of his (paratype) specimens were reared from subimagos, and he describes those subimagos as “quite pale whitish in coloration.”

Size might also be somewhat helpful in distinguishing these specimens from M. m. mediopunctatum (about 7-10 mm at maturity) and modestum (about 8-11 mm at maturity). M. ithaca is about 9-14 mm at maturity. The relatively mature nymph (#764) is at least 11 mm, the female dun (#733) is about 13 mm, and the male dun (#765) is about 11 mm.

When all of these factors are considered, it seems to me that M. ithaca is a more likely ID for the Eastern specimens. (See Bednarik and McCafferty 1979 and Lewis 1974.) I would suggest the following placement for specimens currently in this section:

M. ithaca nymph:
M. ithaca female dun:
M. ithaca male dun:
M. mediopunctatum arwini nymph:
M. mediopunctatum arwini nymph:


ReplyStenonema femoratum male spinner 3 Replies »
Posted by Jmw975 on May 21, 2012 in the genus Stenonema
Last reply on May 21, 2012 by Entoman
Male Stenonema femoratum collected from the Grand River, Ontario. Note the 3 spots at the hind margins of each of the abdominal segments.

(User-posted images are only viewable in the forum section.)
ReplyAdded more Heptagenia culacantha info 12 Replies »
Posted by Troutnut on Dec 19, 2006 in the species Heptagenia culacantha
Last reply on Feb 8, 2012 by Entoman
I went to the entomology library today and photocopied the 1985 paper that first described this curious species. I've updated the culacantha page with this information.
ReplyRed Heptagenia? 30 Replies »
Posted by GONZO on Jul 19, 2011 in the genus Cinygmula
Last reply on Jul 24, 2011 by PaulRoberts
The gills and protruding mouthparts make me think that this might be Cinygmula. I've seen red phase Rhithrogena nymphs, but have never seen this coloration in Cinygmula (or Heptagenia).
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