Dark Brown Spinners

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 and Tricorythodes 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:

• Paraleptophlebia adoptiva is by far the most important species of this genus in the two regions and is an early Spring emerger.


• Paraleptophlebia mollis, Paraleptophlebia guttata, and Paraleptophlebia strigula complement each other in late spring and early summer.


• Paraleptophlebia debilis and Paraleptophlebia praepedita occur together in the fall.

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:

• The most important species is Paraleptophlebia debilis. This large (for the genus) Fall emerger can be found throughout the region. It is often accompanied by one of the slightly larger tusked species. Depending on locale, this can be Paraleptophlebia bicornuta (the most common), Paraleptophlebia packii or Paraleptophlebia helena. Check out their hatch pages for distribution information.


• Spring is the season for the smaller Paraleptophlebia heteronea throughout most of the region with Paraleptophlebia gregalis filling this niche in California and parts of Oregon.

This species is very similar to Drunella flavilinea. In areas where their ranges overlap, they can sometimes be found in the same streams. Allen and Edmunds (1962) say that Drunella coloradensis tends to favor colder water than Drunella flavilinea and that it may emerge as much as a month later.

Anglers in western Wisconsin, where these little flies hatch in good numbers on summer rivers, have termed them "Darth Vaders" because of the very dark color of their wings.

Until recently, this species was known as Serratella deficiens.

This is one of the most important species of the Baetidae family. Previously known as Baetis parvus in the West and its synonym (Synonym: A former name of a taxon, usually a species. Entomologists frequently discover that two insects originally described as different species are one in the same, and they drop one of the names. The dropped name is said to be a synonym of the remaining name. These changes take a while to trickle into the common knowledge of anglers; for example, Baetis vagans is now a synonym of Baetis tricaudatus.) Baetis devinctus in the East, it is distributed across the country but most of its fame comes from excellent hatches in the West. Prior to all the species being combined with Baetis tricaudatus, most angling literature considered it the most populous and widespread western species of the Baetidae family.

Dorsal (Dorsal: Top.) abdominal markings on the nymphs used to differentiate the species in these older works have since proved unreliable. The easiest way to tell them apart from B. tricaudatus is their lack of gills on the first abdominal segment. Telling adults apart is equally tough. Duns of D. hageni are typically a little smaller, but their bodies can also be olive, brownish olive and even two toned with thoraxes a shade of brown or tan with paler olivacious abdomens.

Diphetor hageni has two former names used in angling literature, Baetis parvus in the West and Baetis divinctus in the East.