BWOs

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.

Baetis is probably the most misidentified genus in the angler's mayfly world. Many fly anglers see anything too small to imitate with a size 16 Adams and call it Baetis. In reality, Baetis is the most prominent of several very similar abundant genera in the family Baetidae. It seems every species in the family is perpetually being reclassified, and identifying any of them, even to genus level, is difficult.

The angler who wants to be accurate has two choices. Most people call these flies "Blue-Winged Olives," a name which has lost all meaning because people apply it to several dozen species which mostly have neither blue wings nor olive bodies. It's better to just call them "little (whatever color they are) mayflies." The other good choice is to call them "baetids," the general Latin name for members of the Baetidae family. Many of the specimens on this site can't be keyed below the family level from their pictures alone. The fact is most require observation with a microscope and extensive knowledge of what to look for to make accurate determinations. So the next time a fishing buddy identifies a little greenish mayfly from a distance as Baetis vagans, just smile and nod...