I'll return to this photo -- but first things first. I have just learned from Steven Beaty (Biological Assessment Unit, North Carolina Division of Water Quality) that his "Taxonomy Documents" for North Carolina have now been published online. They can be accessed at: http://portal.ncdenr.org/web/wq/taxonmanual. Separate manuals, in pdf files, are available on 1) The Ephemeroptera of North Carolina, 2) The Plecoptera of North Carolina, 3) The Trichoptera of North Carolina, and 4) The Aquatic Coleoptera of North Carolina. This Biologist's Handbook with Standard Taxonomic Effort Levels, provides detailed keys for family, genus, and species identification of the mayflies, stoneflies, caddisflies, and aquatic beetles that are found in North Carolina.
This is an incredible achievement, and it will probably serve as a standard reference work in the field for many years to come. And, it's available for free! You can even do what I just did -- download it, print it out, and go have it bound for easy use. This is pretty special.
Now, back to the problem of species identification of Maccaffertium flatheads. Dr. Beaty had a look at some of the photos I posted just yesterday -- and thought it unlikely that those nymphs were either M. mediopunctatum or M. Meririvulanum. Why? He's quite sure that there are hairs that follow the spines on the crown of the maxilla. It looks to me like he's right. He was inclined to think -- and I won't hold him to this; that would hardly be fair -- that both nymphs were Maccaffertium pudicum in terms of the species ID.
Now (I can quote him at last!), take a look at what he says on M. pudicum nymphs. "M. pudicum -- nymphs 11-14 mm; lateral projections anterior to 6; 4-8 spines and 15-40 (usually 20-30) hairs on maxillary crown; no denticles on claws; sometimes with dark pattern on anterior edge of abdominal sterna; sterna 5-8 with anterior markings or completely pale. Mountains and Piedmont. Common in smaller streams." ("The Ephemeroptera of North Carolina," p. 20)
Take a look at the photos I posted just yesterday and see what you think. In the meantime, I decided this morning to look into the species ID of the nymph in the photo above. This one was found in a small stream near our home just south of Charlottesville on 11/11/11 (the stream where I took the photos of scuds). Before I had communicated with Dr. Beaty on the nymphs I discussed yesterday, I had reached the conclusion that the nymph in the photo above was probably Maccaffertium pudicum. The evidence: 1) this nymph (and I found three others like it) was 13mm long (BIG), and it's still not fully mature; 2) it does for sure have hair after the spines on the crown, and I can count at least 20; 3) the claws are edentate; 4) there are, for sure, posterolateral projections on all abdominal segments; and 5) there is a dark pattern on the anterior edges of at least some of the abdominal segments. Here are the photos that I took this morning.
1. Maxillary crown -- spines and hairs (I know you can't really count them, but you can make them out.)
2. One of the tarsal claws -- no denticles
3. A ventral view of the nymph, showing the dark anterior edges and the posterolateral projections.
Back to the streams tomorrow where I'll be finding more stoneflies -- and maybe some M. pudicum flatheads (if that's what they are!).
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