There are so many different types of Blue-Winged Olives that they encompass all the major the variability found within mayflies as a whole. Asking, "What time of day does a BWO hatch?" is like asking, "What of day does a mayfly hatch?" or even "What time of day are there bad shows on television?"

BWOs may:

  • Hatch in the morning.

  • Hatch in the evening.

  • Hatch in at midday.

  • Hatch at any time of of year.

The name doesn't even tell us that the flies have blue wings and olive bodies! BWOs may:

  • Have wings in any shade of gray, including bluish gray, but not blue.

  • Have olive bodies.

  • Have brown bodies.

  • Have gray bodies.

  • Have bright green bodies which change color while they're on the water.

But don't we at least know BWOs are small? Yes, except for the big ones, like the several species of Drunella and Attenella that fall under this label. And "small" wouldn't really narrow it down, anyway. The "small" BWOs run in hook sizes from 18 to 28.

Everything about their behavior as a group runs the gamut. They come from completely different types of nymphs, inhabit different types of streams, have different hatching behavior, have very different egg-laying behavior...

Why do we even bother to use such a broad and meaningless category? This is the rule, rather than the exception, for most common names. They're neither specific nor descriptive--the worst of both worlds.

The Latin names don't belong exclusively to scholars; anybody can learn them. And those who don't want to can still be accurate by calling things descriptive names, like "little brown mayfly," rather than lumping everything into a catch-all common name.