Little Iron Blue Quills

This is one of the most prolific genera of mayflies in North American trout streams. Their small size permits the growth of up to three generations per year, and they are good dry-fly insects because they often hatch in impressive numbers and the duns ride the water for a long time before taking flight.

The genus Baetis and its species are probably the most misidentified mayflies in angling. Many who see mayflies too small to imitate with a size 16 Adams call them Baetis, especially if they're olive in coloration. In reality, Baetis (though the most prominent) is only one of several very similar and abundant genera in the family Baetidae. It seems species in the family are perpetually being reclassified, and identifying any of them, even to genus level is difficult. The angler who wants to describe what is seen streamside usually has only four choices:

1. Call them "Blue-Winged Olives" as most do. the problem is this name has lost all meaning due to being applied to dozens of species across several families (many of which have neither blue wings nor olive bodies). Besides, the name was originally coined for a species of British ephemerellid, the family where this common name should properly reside.

2. Call them "baetids", the Latin name for referring to members of the Baetidae family as a group. While technically accurate scientifically, it doesn't tell the listener or reader much about their appearance.

3. Call them outmoded scientific names - Even calling them by the updated name is usually risky for most species in the field. Adding to the difficulty by using names from outdated nomenclatures? Talk about confusion...

4. Call them "little (whatever color they are) quills." Perhaps this is the best choice as at least it's more accurately descriptive.

The fact is many are so similar that even alot of the specimens in the hatch pages can't be keyed below the family level with absolute certainty; at least from what's observable in the photos alone. They often require observation with a microscope and extensive knowledge of the subtle differences for accurate determinations. So - the next time a fishing buddy identifies a little olive mayfly from a distance using an obsolete name like Baetis vagans, just smile and nod...

For anglers raised on Schwiebert, Swisher, etc., it is often difficult to locate many important species in the newer literature. When working with older taxonomies and/or angling texts, the following hatch page links may prove helpful:

Baetis devinctus = Diphetor hageni (can be an important eastern species)
Baetis hiemalis = Baetis brunneicolor (important Midwest species with a national distribution)
Baetis insignificans = Acentrella insignificans (can be important in some western locales)
Baetis parvus = Diphetor hageni (very important western species)
Baetis propinquus = Labiobaetis propinquus (important in the West with a national distribution)
Baetis pygmaeus = Acerpenna pygmaea (can be important with distribution across all regions)
Baetis vagans = Baetis tricaudatus (most abundant and important species nationwide)

The relatively new genus Fallceon has two species of interest that are made up of several previous Baetis species. They are distributed nationally and may prove significant as more is learned about the angling opportunities they present, especially in the the South and Southwest.

This genus contains only one species of interest to anglers, Labiobaetis propinquus. See the species hatch page for more information.

The species of this genus can be identified by the combination of its tiny elliptical hindwings lacking costal projections (

The costal projection of a Baetidae dun.

Costal projection: A bump or point sticking up from the front margin of an insect's wing, usually the rear wing of certain mayflies. It is sometimes called a costal process.) ( a few obscure species have them but they are so reduced as to be barely observable under low magnification) and lacking a conical mesonotal projection (Conical mesonotal projection: small cone shaped spike sticking up from the top and front part of the middle thorax segment.). Their two tailed nymphs are more difficult.

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.

This species was previously known as Baetis propinquus, a name from older nomenclatures and angling literature familiar to many western anglers. Prior to its current listing, it did a brief stint in the genus Pseudocloeon. The irony is that though this species has hind wings, it was the last species remaining in Pseudocloeon (before the genus recent Nearctic taxonomic demise) which was best known for its species lacking hind wings as an identifying character.

Though it has a national distribution its most important hatches occur in the West, usually hatching between the larger broods of Baetis tricaudatus. Western anglers experiencing a hatch can easily confuse them with the larger Baetis bicaudatus as both nymphs appear similar with only two tails. Besides size, the adults can be separated from bicaudatus (with the help of a little magnification) because L. propinquus lacks acute costal projections (

The costal projection of a Baetidae dun.

Costal projection: A bump or point sticking up from the front margin of an insect's wing, usually the rear wing of certain mayflies. It is sometimes called a costal process.) on its tiny hind wings. Conversely, the presence of hind wings and lack of conical mesonotal projections (Conical mesonotal projection: small cone shaped spike sticking up from the top and front part of the middle thorax segment.) makes them easy to tell from the more common and equally tiny Acentrella turbida.

Baetis tricaudatus is undeniably the most widespread and abundant baetid on the continent and arguably the most important mayfly species to trout and anglers alike. Eastern anglers used to know these important mayflies by the storied name of Baetis vagans. Conversely, the usually much larger and late Fall hatching brood of Baetis tricaudatus was considered an important Western species with its own tradition. But, entomologists recently determined that they are both in fact the same species. The nomenclature conventions guiding entomologists do not account for a name's regional fame among fishermen, and new or obscure species names may replace their old favorites. Sometimes taxa with disparate traditions are combined. Baetis vagans is one such casualty. Fortunately, trout think like Shakespeare: A rose by any other name would smell as sweet. The rose that was vagans has lost none of its charm. This species is multibrooded (Multibrooded: Producing more than one generation in a single year. Baetis mayflies are a classic example. Insects which produce a single generation with two distinct peaks (like the June and September hatches of Isonychia bicolor mayflies) are not multibrooded, because the fall insects are offspring from the previous fall instead of the current year's spring.) with the hatches of Spring being larger flies. As the weather warms the following broods are composed of progressively smaller flies. In the East, they range in size from 16 to 20. In the West, they may run a size larger.