Mayfly - Arthroplea bipunctata

Moved

Such minor differences even put it in a different family. Lloyd, thanks for going the extra mile to get this corrested.

… tom murray, 10 August, 2009 - 9:10am

My pleasure, Tom

This unique family, which has only one Nearctic representative, was the missing link in putting this right. I've had misgivings about the hind wing shape for some time. (It should be more rounded in Choroterpes and with more of a "bump" instead of a sharp angulation.) Working under the assumption that a tail was not missing led me to consider heptageniid possibilities with no joy. Eventually, I remembered that Arthroplea was once placed in Heptageniidae, but descriptions of the adults are few and far between, and images are even harder to find. It was a photo of the European version (Arthroplea congener) from a 1975 DDR nature journal article that finally connected all the dots. My German is terrible, but the picture was worth a thousand words. :)

… Lloyd Gonzales, 10 August, 2009 - 11:39am

Correction: Arthroplea bipunctata

McDunnough's original 1924 description of this species helped to solve the problem of the "missing" tail and other nagging inconsistencies. He concludes his description with these comments:
"This species has a superficial resemblance to Choroterpes basalis....The specimen serving for the slide of the genitalia would appear to have an extra joint in the forceps but I presume that this is an abnormal condition."
The unusual nymphs of this species had not been described or associated at the time of McDunnough's description, and the presumed "abnormal condition" of the forceps was actually one of the unique traits of A. bipunctata males. The distinctive forceps with three small terminal segments can be seen by enlarging this photo of your specimen.

… Lloyd Gonzales, 7 August, 2009 - 7:46pm

Thanks Lloyd

If one of the side tails fell off, it would be easy to tell. It figures the middle tail is the one missing:-)

… tom murray, 29 May, 2009 - 5:17pm

My best guess...

is that this is a male Choroterpes basalis subimago. Although it has the look of a leptophlebiid and a hindwing costal angulation that rules out Leptophlebia and Paraleptophlebia, I was thrown by the absence of the middle "tail." When I checked your other specimens that I had suggested were C. basalis, I noticed that each of them was missing one or two tails. Tail loss seems to be a chronic hazard with this species. :)

… Lloyd Gonzales, 29 May, 2009 - 3:05pm