Here’s a challenge for you, should you choose to accept it: name the bug below.
And here are some clues.
As a youngster, it lives in water like this for two or three years.
Then in September or October it crawls ashore, transforms, and hangs out along the shoreline without eating for two or three weeks, all the while looking for a mate. This one
emerged and eventually encountered my camera a fortnight ago. If our bug is a female like this, before long it will sport a full egg sac on its rear end, and be ready to deposit it in
the water and start the cycle over again.
If you answered that it’s a stonefly, you are largely correct. And you are probably a fly fisher. Fly fishers generally know more about bugs, particularly those associated with water,
than most people would consider normal.
But now the hard part: what
kind of stonefly is it?
Even a fly fisher would rarely get this answer right. Hardly anyone, fly fisher or otherwise, has heard of the bug you see here, the Cascades Stonefly; even though at about 1.5
inches long, it rivals in size the storied salmonfly, one of the largest and best known stoneflies in North America. There are very few pictures of the Cascades Stonefly on the
internet; this may well be the only one showing a female with an egg sac. It lives in higher elevation, cold, fast streams and rivers, mostly in the Cascade Mountains; with some
spreading south to the Sierra Nevadas and east to the edge of the Rockies. And its “common” name is not really common at all, since it’s not well enough known to have a generally
accepted common name. Instead, the name “Cascades Stonefly” was
assigned some years ago by an entomologist who cataloged stoneflies, as a more easily remembered moniker
than its scientific name,
Doroneuria baumanni.
And what about those bug eyes? Like all insects, these stoneflies sport compound eyes, made up of hundreds or thousands of ommatidia stacked side by side, and are visible in the
close-up below.
Each ommatidium is like a small telescope, with a lens on the outer end of a slender tube, and photoreceptor cells on the other, internal end to capture the signal. Together the many
ommatidia provide an excellent image to the little brain of these bugs, though it is no doubt different in some respects from the image we would see for the same scene. I’ve always
thought how interesting it would be if we could somehow redirect the image information from a bug’s eyes to our brains, to see just what it looks like. Who knows, maybe someday
it will be possible.
