Actually, isn't the male Hex limbata smaller and dark reddish brown, like the photo?
Right, John, though the males do vary quite a bit as well. And the atrocaudata
hatch timing is
usually later than limbata
, with some overlap in many places. The atrocaudata
often have dark staining around the rear margin of the hind wings, but this seems variable and is absent in some males I've observed. (And I often see photos identified as limbata
that also have this staining.)
My most useful field ID trait for atrocaudata
is to look for the dark, paired longitudinal dashes on the dorsal surface at the rear of the abdomen (between the angled hashmarks that meet the lateral midline). These paired dorsal dashes continue only faintly over the rest of the abdomen in some specimens, but they are usually very distinct on segments (7), 8, and 9. On rigida
and many limbata
, these marks are replaced by single, thicker dashes that form a "trident" shape in conjunction with the angled hashmarks, and can also be most prominent at the rear of the abdomen. Rigida
is the palest of the three, but this alone is not a reliable distinction because limbata females can also be very pale in some locations. The shape of the "nose" in the nymphs and the distinctive shape of the male "organ" are about the only ways I know to confidently distinguish beween rigida
Do I read things correctly that it was taken in a river in Maine? Do you guys get hex up there?
Nightfisher, although not as famous as the Midwestern activity, Maine does have good Hex hatches, as do NY, PA, and many other Eastern states. Eastern Canada also has good hatches. Limbata
is a transcontinental species, contributing good Hex activity to the West and most other parts of the country. Perhaps the greatest variety of Ephemeridae species is found in the upper Southeast and Mid-Atlantic States, with four Hex species and relatives like Litobrancha
, and several Ephemera
species contributing to a great wealth of big Ephemeridae drakes there.