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Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

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

This page only contains pictures of specimens.

To read about Heptageniidae, visit Page 1.

Specimens of the Mayfly Family Heptageniidae

13 Male Duns
15 Female Duns
15 Male Spinners
15 Female Spinners
15 Nymphs

10 Streamside Pictures of Heptageniidae Mayflies:

11 Underwater Pictures of Heptageniidae Mayflies:

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?
M. ithaca in M. mediopunctatum section?
3 replies
Posted by GONZO on Sep 1, 2012 in the species Stenonema 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: http://www.troutnut.com/specimen/764
M. ithaca female dun: http://www.troutnut.com/specimen/733
M. ithaca male dun: http://www.troutnut.com/specimen/765
M. mediopunctatum arwini nymph: http://www.troutnut.com/specimen/573
M. mediopunctatum arwini nymph: http://www.troutnut.com/specimen/574


Stenonema 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.

Added 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.
Red 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).

Start a Discussion of Heptageniidae


  • Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.
  • Mayo, V.K. 1952. New Western Ephemeroptera, IV, With Notes. The Pan-Pacific Entomologist 28(4): 179-186.
  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.
  • Slater, J. and Kondratieff, B.C. 2004. Review of the Mayfly Genus Cinygmula McDunnough (Ephemeroptera: Heptageniidae) in Colorado. Journal of the Kansas Entomological Society 77(2): 121-126.

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

Family Range
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