Stillwater Mayflies

[Taxon]

During the summer of 2007, biotic sampling was conducted in (1243) representitive lakes and reservoirs across the (48) contiguous states by individual state agencies. The biotic samples were identified to the lowest practical taxonomic level and counted by the US Environmental Protection Agency (EPA).

The below table Iists the mayflies nymphs collected from representative lakes and reservoirs across the US:

Order (Family Common Name)	Taxon	Level
Ephemeroptera (Armored Mayfly)	Baetisca	Genus
Ephemeroptera (Cleftfoot Minnow Mayfly)	Siphloplecton	Genus
Ephemeroptera (Common Burrower Mayfly)	Ephemera	Genus
Ephemeroptera (Common Burrower Mayfly)	Ephemeridae	Family
Ephemeroptera (Common Burrower Mayfly)	Hexagenia	Genus
Ephemeroptera (Flatheaded Mayfly)	Ecdyonurus	Genus
Ephemeroptera (Flatheaded Mayfly)	Epeorus	Genus
Ephemeroptera (Flatheaded Mayfly)	Heptageniidae	Family
Ephemeroptera (Flatheaded Mayfly)	Leucrocuta	Genus
Ephemeroptera (Flatheaded Mayfly)	Maccaffertium	Genus
Ephemeroptera (Flatheaded Mayfly)	Rhithrogena	Genus
Ephemeroptera (Flatheaded Mayfly)	Stenacron	Genus
Ephemeroptera (Flatheaded Mayfly)	Stenonema	Genus
Ephemeroptera (Little Stout Crawler Mayfly)	Leptohyphidae	Family
Ephemeroptera (Little Stout Crawler Mayfly)	Tricorythodes	Genus
Ephemeroptera (Mayfly)	Ephemeroptera	Order
Ephemeroptera (Pale Burrower Mayfly)	Ephoron	Genus
Ephemeroptera (Pale Burrower Mayfly)	Polymitarcyidae	Family
Ephemeroptera (Primitive Minnow Mayfly)	Ameletus	Genus
Ephemeroptera (Primitive Minnow Mayfly)	Siphlonurus	Genus
Ephemeroptera (Pronggill Mayfly)	Choroterpes	Genus
Ephemeroptera (Pronggill Mayfly)	Leptophlebia	Genus
Ephemeroptera (Pronggill Mayfly)	Paraleptophlebia	Genus
Ephemeroptera (Pronggill Mayfly)	Thraulodes	Genus
Ephemeroptera (Pronggilled Mayfly)	Leptophlebiidae	Family
Ephemeroptera (Small Minnow Mayfly)	Acentrella	Genus
Ephemeroptera (Small Minnow Mayfly)	Apobaetis	Genus
Ephemeroptera (Small Minnow Mayfly)	Baetidae	Family
Ephemeroptera (Small Minnow Mayfly)	Baetis	Genus
Ephemeroptera (Small Minnow Mayfly)	Callibaetis	Genus
Ephemeroptera (Small Minnow Mayfly)	Camelobaetidius	Genus
Ephemeroptera (Small Minnow Mayfly)	Centroptilum	Genus
Ephemeroptera (Small Minnow Mayfly)	Fallceon	Genus
Ephemeroptera (Small Minnow Mayfly)	Paracloeodes	Genus
Ephemeroptera (Small Minnow Mayfly)	Procloeon	Genus
Ephemeroptera (Small Minnow Mayfly)	Pseudocentroptiloides	Genus
Ephemeroptera (Small Minnow Mayfly)	Pseudocloeon	Genus
Ephemeroptera (Small Squaregill Mayfly)	Brachycercus	Genus
Ephemeroptera (Small Squaregill Mayfly)	Caenis	Genus
Ephemeroptera (Spiny Crawler Mayfly)	Dentatella	Genus
Ephemeroptera (Spiny Crawler Mayfly)	Drunella	Genus
Ephemeroptera (Spiny Crawler Mayfly)	Ephemerellidae	Family
Ephemeroptera (Spiny Crawler Mayfly)	Eurylophella	Genus
Ephemeroptera (Spiny Crawler Mayfly)	Serratella	Genus
TOTALS	44

Surprisingly, the most frequently collected mayfly genus exceeded the second most frequently collected genus by a ratio of 6:1.

So, which of the above mayfly genera would you guess was most frequently collected?

 

[Mark Melton]

Just a guess, but I'd say Ephemera or Hexagenia.

 

[Taxon]

Hmm, guess it's time for a hint. Did anyone think to google Lakes Biotic Survey?

 

[Mark Yoshida]

Cheated and looked but I cheated once in school and was still wrong.

Ephemeroptera (Small Squaregill Mayfly)

Caenis

Genus

712​

0​

0​

0​

712​

 

[Taxon]

Cheated and looked but I cheated once in school and was still wrong.

Ephemeroptera (Small Squaregill Mayfly)

Caenis

Genus

Well Mark, you weren't wrong this time. Congrats.

 

[Mark Melton]

i guess that's one reason for surveys. I would've never gotten Caenis or the second one Callibaetis.

 

[Taxon]

i guess that's one reason for surveys. I would've never gotten Caenis or the second one Callibaetis.

I suspect burrower mayflies like Ephemera and Hexagenia may have been far less accessible to those doing the collecting, but who knows.

 

[Chucker]

I suspected that it would be caenis. The number of them that can hatch at one time can be truly astounding. I suspect, though, that if it was done by weight that Hexagenia would be up there.

 

[Taxon]

I suspected that it would be caenis. The number of them that can hatch at one time can be truly astounding. I suspect, though, that if it was done by weight that Hexagenia would be up there.

Have we by chance met?

 

[Chucker]

I don't think so. I used to work on marine fish and crustaceans, my interest in freshwater entomology is purely amateur!

 

[Taxon]

I suspected that it would be caenis. The number of them that can hatch at one time can be truly astounding.

Exactly. I remember watching an apparent hatch one evening at dusk on what (at the time) was my favorite east-of-the-Cascades lake. Of course, I couldn't actually see what was hatching. But, by standing on some elevated ground above the launch, I had a clear view of a perhaps 100-yards-diameter piece of a water in the bay to the left of the launch. There was not a breath of wind, so it was smooth as a mirror, except there were so many fish rising partly out of the water, that it simply boggled one's imagination.

It wasn't until we started loading my fishing partner's vehicle that we began to understand what we had just witnessed. There were perhaps a dozen tiny mayflies on the windows of the vehicle. And, the freshly emerged subimago would land, then almost immediately begin its final molt to imago, which as I recall, took less than a minute, and then fly off, occasionally even towing its subimaginal shuck in flight.

Luckily, I was able to capture several of those tiny mayflies. Upon getting home, those mayflies were put them under the magnification of a loupe, and identified as being of genus Caenis. So, that's my story, and I'm sticking to it.

 

[RCF]

@Taxon I hope you are having as much fun as we are learning. Glad you are participating !

 

[Taxon]

@Taxon I hope you are having as much fun as we are learning. Glad you are participating !

Thanks, RCF. I'm as happy as a clam at high tide.

 

[tkww]

I've only been present for one Caenis hatch, and unfortunately it wasn't on a "lake"--it was really a river outflow--that had much in the way of fish in it. Or at least fish that would rise to the hatch. But wow, the numbers were mind-boggling.

 

[Taxon]

Hi tkww-

Very neat. What was that reddish surface they were on? Was the surface horizontal or was it vertical? What time of day did it occur?

 

[GAT]

I love the common names of some of the bugs. Many do not sound Mayfly-ish in the least.

 

[Taxon]

I love the common names of some of the bugs. Many do not sound Mayfly-ish in the least.

Examples?

 

[tkww]

Hi tkww-

Very neat. What was that reddish surface they were on? Was the surface horizontal or was it vertical? What time of day did it occur?

Vehicle surface, vertical surface orientation I believe, and mid-late afternoon. Dated May 15.

 

[Taxon]

Vehicle surface, vertical surface orientation I believe, and mid-late afternoon. Dated May 15.

Well, that closely corresponds to my experience with a Caenis emergence. In your photos, I assume all but those with obvious wings are subimaginal exuviae. Is that correct?

 

[tkww]

I assume all but those with obvious wings are subimaginal exuviae. Is that correct?

Yes. What time of day would their emergence from the water likely have been?