This common name refers to only one genus.
These are often called Paraleps.
There are many species in this genus of mayflies, and some of them produce excellent hatches. Commonly known as Blue Quills or Mahogany Duns, they include some of the first mayflies to hatch in the Spring and some of the last to finish in the Fall.
In the East and Midwest, their small size (16 to 20, but mostly 18's) makes them difficult to match with old techniques. In the 1950s Ernest Schwiebert wrote in Matching the Hatch
"The Paraleptophlebia hatches are the seasonal Waterloo of most anglers, for without fine tippets and tiny flies an empty basket is assured."
Fortunately, modern anglers with experience fishing hatches of tiny Baetis
mayflies are better prepared for eastern Paraleptophlebia
. It's hard to make sense of so many species, but only one is very important and others can be considered in groups because they often hatch together:
In the West, it is a different story. For starters the species run much larger and can be imitated with flies as large as size 12, often size 14, and rarely smaller than 16. Another difference is the West has species with tusks! Many anglers upon first seeing them think they are immature burrowing nymphs of the species Ephemera simulans
aka Brown Drake. With their large tusks, feathery gills, and slender uniform build, it's an easy mistake to make. Using groups again:
Female Paraleptophlebia debilis (Mahogany Dun) Mayfly Dun
View 3 PicturesSize: 9mm. These photos really highlight the brown pigmentation of the wing venation (Venation: The pattern in which the veins on the wings of an insect are arranged. It is usually one of the most useful identifying characteristics.), but in the hand the wings look to be a uniform smokey gray. - Entoman