The Stream Doctor

February 16th, 2004

Email YOUR Questions directly to the Stream Doctor. This is your opportunity to get an experts professional opinion on anything stream related.

Q. I read an article in a fly fishing magazine written by a man named Al Caucci (of the Delaware River Club) in which he made reference to a mayfly he calls Ephemerella "X". This species is related to E. subvaria and is also referred to by Mr. Caucci as the Dark Hendrickson. (He included that name for the benefit of us fly fisherman, as the term Dark Hendrickson has no scientific meaning, as you know).

I have never seen any other reference to this mayfly in any other publication. Did he discover a new species or is E."X" some other previously identified mayfly that he misidentified? Who decides what is or isn't a new insect species and what it's Latin name will be? Are there debates in the entomology world over how to classify different insects? Have there been any new mayfly species discovered recently?

A. Response: These are excellent questions, and I will address them in order.

Regarding Ephemerella "X." Now I do not know what Mr. Caucci intends by his use of this term, but I will explain its use in the scientific literature, which is probably the same. Remember that the identification of adult mayflies to the species level is well known; the problem is that we simply do not have the knowledge to identify all of the nymphs to species. Thus, you will often see in species lists from a particular stream a list which may include, for example, Baetis vagans, Baetis sp. a, and Baetis sp. b, with the appropriate data after each name. What this indicates is that the scientist had three different Baetis species in his stream - one that could be positively identified as B. vagans, and two that were definitely of the genus Baetis, different from each other, but not identifiable to the species level. He may further indicate that further studies were being undertaken to either (1) rear the two unidentified species to adults so that they could then be positively identified, or (2) have the two unidentified species examined by an expert taxonomist who might, or might not, be able to identify them to species. In some cases, it is entirely possible that an unidentified species might turn out to be a new species; this happens frequently, especially if the specimens are from a little studied area or type of habitat. I suspect that Mr. Caucci was simply using "x" as I did "sp. a." In 1976, Edmonds, Jensen, and Berner listed 28 different species of Ephemerella. Further, since most of these are only identifiable from adults, I tend to be a bit hesitant before accepting species identifications of immatures unless I know that the person has the necessary equipment and knowledge to determine these. This isn't meant to suggest that Mr. Caucci doesn't know his business; I just get uneasy when most of the fishing literature always seems to have E. subvaria listed, whereas this species only is known from the Northeast and Central U.S. Why don't fishermen ever find any of the other 27 species? Enough of that bandwagon.

Your second question about whether it is a new species or a previously misidentified mayfly has probably been answered by the above. It could be a new species or one that Mr. Caucci knew was of the genus Ephemerella, but a different species from what he knew to be E. subvaria.

New species can be described and identified by anybody, although you better have some good credentials in taxonomy for that particular group of insects. There are many scientists who have devoted their careers to sorting out the taxonomy of a particular group, and it is usually these folks who decide, or at least are consulted, when a new species is suspected. There is an extensive protocol to doing this and it includes publishing the complete description and measurements of the insect in certain languages, description of the habitat where it was found, where the original specimen is stored, etc., etc. The Latin name for the species, too, is selected by whoever is describing the new species and is sometimes named to honor somebody, or a place, or something descriptive of the organism. This leads into your next question about debates. It may be that a newly found insect may not even fit into one of the existing genera or families, and in this case, it will not only be a new species but also a new genus and, perhaps, family. There are taxonomists, as I pointed out above, who do nothing but study, evaluate, and determine the correct lineages of various insect groups. Further, it is not uncommon for a person to decide that based on his extensive studies, he has decided that major changes are necessary in the groupings. Perhaps a family that contained 7 genera should be revised into two families with 4 genera in one and 3 in the other. Or maybe a subfamily or superfamily needs to be established to sort things out. New family or other names may be needed. This goes on continuously and is undergoing major changes now. This is because up to fairly recent times, all of this was done on morphological, behavioral, and evolutionary characteristics. Now, DNA analyses are showing that previously established relationships may or may not be valid. It is causing considerable consternation in the scientific community, especially for the poor field ecologist who formerly could do a pretty good job with a microscope and the correct keys, but now needs a DNA analytical lab. You can't take that into the field with you.

I don't know how many new species of mayflies have been discovered recently, but you can be sure that it is happening. There are more than 700 species of mayflies identified from North America north of Mexico, so you can see that the folks who like to variously lump and split these into different groupings have enough work to last several careers.

You've probably now read more than you ever wanted to on the subject, but you got me going on a subject that has no easy, short answers. If I've just further confused the issue, let me know and I'll try to clarify things for you.

If you have a question, please feel free to contact me.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584

The 'Stream Doctor' is a retired professional stream ecologist and author, now living in the West and spending way too much time fly-fishing. You are invited to submit questions relating to anything stream related directly to him for use in this Q & A Feature at

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