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Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large Brown Trout that only touch streamers for the rest of the year.

Mayfly Genus Leptophlebia (Black Quills and Blue Quills)

Leptophlebia mayflies do not generate superhatches, but their medium-large size and other properties make them a relevant part of the early season.

The information below was mostly discovered in Leptophlebia cupida, the most important species, but it is not known to differ in the others.

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.

Hatching behavior

Time of day : Sporadic from midday through evening, usually peaking near midday

Water temperature: 55°F and up

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

Time of day: Afternoon and evening

Habitat: Medium to fast water

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

Current speed: Slow

Substrate: Silt, detritus, leaf drift

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.

Specimens of the Mayfly Genus Leptophlebia

1 Male Dun
Male Leptophlebia cupida (Black Quill) Mayfly Dun
This Leptophlebia cupida dun was extremely cooperative, and it molted into a spinner for me in front of the camera. Here I have a few dun pictures and one spinner picture, and I've put the entire molting sequence in an article.
1 Female Dun
Female Leptophlebia (Black Quills and Blue Quills) Mayfly Dun
I collected this mayfly after user Al514 tipped me off to the presence of some Leptophlebia mayflies I didn't seem to have yet with his ID request of a male dun. This seems to be of the same species. I also collected a female spinner. Based on that spinner, I can tell that this is either Leptophlebia cupida or Leptophlebia nebulosa, but I can't tell which.

Unfortunately none of the specimens I collected made it through the hot, sunny day very well. So the pictures aren't great, but they're better than nothing.
5 Female Spinners
13 Nymphs

Recent Discussions of Leptophlebia

Posted by Steamntrout on Jun 14, 2017 in the species Leptophlebia nebulosa
Last reply on Jun 14, 2017 by Steamntrout
Looking at Purdue's May Fly Central it shows nebulosa being found in Canada's Far North, North East and North West as well as USA's North East, South East & Far West.
Southeast Mayflies
24 replies
Posted by DarkDun on Nov 20, 2006 in the species Leptophlebia cupida
Last reply on Mar 4, 2007 by Taxon
This is one of the species that seem to be prevalent in our area of southwest NC. It emerges in March as I recall and again in October on certain streams. I would like to confirm that this next season.

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» Genus Leptophlebia (Black Quills and Blue Quills)
Species in Leptophlebia
Leptophlebia cupidaBlack Quill1773
Leptophlebia johnsoniBlack Quill00
Leptophlebia nebulosaBlack Quill00
4 species (Leptophlebia bradleyi, Leptophlebia intermedia, Leptophlebia konza, and Leptophlebia pacifica) aren't included.
Genus Range
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