crepuscular wrote:
Chaz wrote:
They are too small to be drakes, look at the size of the bug compared to the guys hand and fingers. Not even big enough to be a MB.
Well I'd have to disagree with that assessment. First you have to consider camera angle. Then the same approximate distance on my hand the from the same portion of the finger as in the photo of the mayfly is almost 18mm, and I do not have a giant hand or a small one, pretty much average size. The size range for most of the
Ephemera varia that we have here in PA is from 13-20 mm. The specimen in question fits in that size range. These mayflies like most of the Ephemerids have very large size ranges. For example look at a female green drake from Penns compared to a male from Pine or Kettle creeek there's a big difference. My records show that the
E. varia from the yellow breeeches that I have collected have a size range from 15-18 mm for the males and 17-21mm for the females. The free stone versions are much smaller, so although size may be a distiguishing characteristic, it may not be the most relaiable one. A size range may be a better one. The next character to look at would be the head. In the fuzzy photo you can still see that the eyes are wide set and the head is not flattened like that of a heptageniid mayfly. Instead the head is small in proportion to the metanotum again fitting the description of the Ephemerids. The abdominal markings look to be a close fit the description of Needham, 1920, 1935, and Burks 1953 for
Ephemera varia. There are no heptageniids with adult abdominal markings like this. The dark markings on the crossviens also fit the description of
Ephemera varia again see Needham 1920, Needham 1935, and Burks 1953. The fore legs have the banding at the joint of the femur and tibia, again fitting the description of
E. varia. And then you have the timing, which as well all know is not a great way to identify a mayfly, but
in general, it's yellow drake time in PA.
As to how to tell the difference between
E.. varia and
E. guttulata the obvious difference in the dun statge is the overall coloring of the mayfly dorsal abdominal markings. In general, because again there is a lot of variation in the coloration of mayflies, the
E. guttulata will be darker in coloration with a slight green hue in the wings and a yellow creamy coloration to the ventral side of the abdomen in the dun stage than the more lighter creamy whitish yellow of
E. varia.In
E. guttulata the dorsal side of the abdomen will be a dark continuous band running the whole lenght of the abdomen. In
E. varia the dorsal abdominal portion of the mayfly will have a series of dark markings with a lighter medial stripe along the entire abdomen. In the spinner stage the dorsal stripe on
E. guttulata is not there and the abdomen is without marking for the most part. The dorsal portion of the abdomen retains the markings of the dun stage in
E. varia.