Mayfly Genus Leptophlebia (Black Quills)

Where & when

Caucci and Nastasi in Hatches II tell an interesting story of their unsuccessful search for fishable populations of Leptophlebia nymphs. I have had better luck. They searched during the time when these nymphs are supposedly concentrated in schools in preparation for emergence; this may be exactly why they did not catch any. If the nymphs abandoned most of their habitat to gather in schools, they would be hard to find without some luck to stumble upon one of the schools. I have sampled good populations of Leptophlebia cupida from prime trout water during January and February, when they were more spread out.

In 148 records from GBIF, adults of this genus have mostly been collected during April (31%), June (26%), May (20%), July (11%), and March (8%).

In 37 records from GBIF, this genus has been collected at elevations ranging from 3 to 8871 ft, with an average (median) of 2969 ft.

Hatching behavior

The duns usually emerge laboriously at the surface. Fred Arbona notes in Mayflies, the Angler, and the Trout that they swim to and from the surface for an hour before they emerge, a habit usually found in the Ephemerellidae family.

Some authors report that they occasionally crawl out onto shore to emerge.

Spinner behavior

Most sources say the spinners lay their eggs over fast water, but I have watched them over smooth-water runs of medium current speed, too. The females rise and fall over the water to oviposit, dropping some eggs as they contact the surface at the bottom of each dive. As they fall they lock their wings in a V-shaped position and look like little airplanes dive-bombing the surface.

When they fall spent or get stuck on the surface during egg-laying, they are taken eagerly by trout. To my knowledge these spinner falls are never very intense, but they can get the trout rising. I have seen it on a little farmland brookie stream in Wisconsin.

Nymph biology

Although Leptophlebia cupida nymphs are universally described as slow-water dwellers, I have also found good concentrations in strong riffles. They probably reside in slow microhabitats near the bank and in pockets in these fast stretches of the river.

These nymphs are known for gathering in schools like little minnows and migrating for distances up to a mile through the slow shallows of a river before emerging. The word "migration" is overused in angling entomology books to describe the pre-emergence activities of many species, but this is one of the only mayflies for which the word is no exaggeration.

Some authors say that Leptophlebia nymphs are poor swimmers, but I have found the opposite. They are a notch slower than the true swimmer families, but they swim much faster and more gracefully than other crawlers or clingers like Ephemerellidae and Heptageniidae. If they were as slow as some suggest, their lengthy migrations would be difficult to believe.

Because the nymphs are especially tolerant of warm, slow-flowing water, they make excellent aquarium mayflies. They are good species to take to the science classroom, where they can survive in a goldfish bowl with a few leaves in it and are likely to emerge before the end of the spring term.

In the wild, the nymphs are mostly nocturnal.