Thursday, June 27, 2013
Serratella carolina/Serratella serrata: additional comments
The Serratella spiny crawlers that I found yesterday will be listed in our EPT list as "Serratella serrata/Serratella carolina." This is why.
1. Serratella carolina was "synonymized" (i.e. equated) with Serratella serrata by Jacobus and McCafferty in 2003. (Jacobus, L.M. and W.P. McCafferty, "Revisionary contributions to North American Ephemerella and Serratella (Ephemeroptera: Ephemerellidae)," Journal of the New York Entomological Society, 111 (4), pp. 174-193.) Beaty tells me that NC has not yet accepted that equation, but it very well may -- and soon.
2. The two species are distinguished in the following ways.
a) Both species have tubercles on the pronotum, but occipital tubercles are distinct on S. carolina while on S. serrata, if they are present, they're "indistinct." This is the photo I posted in the previous entry showing the tubercles on the nymph in the photo at the top of the page.
Beaty has looked at this photo and says that he can't really tell if the occipital photos are really "distinct," for that we would need a lateral view. From what I can see with my microscope, those bumps don't really stick out from the head in a lateral view. This is a call I can't make for sure.
b) S. carolina has tubercles on abdominal terga 3-9; S. serrata has them on 3-8. As I noted yesterday, I "think" I can see them on tergite 9 on our nymph -- but I'm not really sure. If they're there, they don't stick out in a prominent way, and -- and this is important -- in an article by Jacobus and McCafferty published in 2000 in which they demonstrate variation in the abdominal tergites for S. serrata, some of their figures (see 2 and 6) show "wavy" posterior edges on tergite 9. (Jacobus and McCafferty, "Variability in the larvae of Serratella serrata (Ephemeroptera: Ephemerellidae)," Entomological News 111 (1), pp. 39-44.) They look the same as those in this photo.
c) The caudal filaments of S. serrata have "intercalary hairs," those of S. carolina do not. This is a tough one, but I do think I can see intercalary hairs on the tails of our nymphs. They are too fine and too few in number for me to get a microscope photo -- but they are there. Beaty tells me there are only a "few."
For all of these reasons, I've decided to label this species "Serratella serrata/Serratella carolina." If North Carolina (Beaty and the BAU) changes its mind on seeing the two species as one, I'll let you know.