I am dubious that they are the same species through this long cycle as some of these reports seem to imply.
This is an interesting post to me. I think first off we need to admit that we are still as infants when it comes to really having a handle on what's going on out there with these bugs.
Assuming, just for arguments sake, that it is the same species in the lake, in the stream, larger or smaller versions, variations in shades, emerging as the season progresses, etc...What would account for these differences? Different minerals or food types available? What? We know that different stretches of a stream could show differences in alkalinity, chemical makeup, average temps, and so on...These critters have been around a long, long, time...Could it be that the mayfly has adapted/evolved in a particular way to these different environments? How much from the original does a bug have to change before we classify it as a different species?
I looked up "race" in a Webster's and read the following, "an actually or potentially interbreeding group within a species, also, a taxonomic category(as a subspecies) representing such a group." I'm a Homo sapien according to the folks crafting this puzzle/chart and can travel the globe and mate with other Homo sapiens and father offspring and it doesn't matter if the female is Caucasian, or any other shade, she has buck-teeth, or is shaped or looks like me in any similar way...
I guess what I'm asking then, is this, is this what we are talking about with these variations we find? Something akin to different races? Will it end up something like, for example, E dorothea dorothea central michigani vs E dorothea dorothea UP michigani? (we all know I made this up)...
If we found a species that we considered the same but different (larger, smaller, pinker, bluer, whatever)...Would they be able to mate? Do they mate? Could this lead to even more differences? Or the differences we seem to be observing?
I'm not sure if any of this makes any sense or not and I'm not trying to be funny here...Just wondering how others here reconcile these differences that we all have heard of and you mentioned with the science here...Forget for the moment the angling side of it which tosses a whole other wrench in to the mess.
On a lighter note though regardings Matt's original question about egg sac color...We all know he's going to catch more than his share of trout no matter what color he decides on...:) I may have told the story here before about my step-father dying women's shoes at his shoe repair shop and he is actually color blind...Somehow he would follow a recipe for the color and from the "tone" of the color seemed to always get it right...
I agree with Roger...When in doubt ask Ernie
Ernest Schwiebert described Ephemerella dorothea dorothea ova as golden yellow, and Ephemerella excrucians ova as yellowish.
"You say po-tay-toe and I say po-ta-toe...Let's call the whole thing off!" :)