Jumpin' Bristletails! Slitherin' Stimulopalpus!

Every now and then, I have fresh cause to celebrate the Kaufman Field Guide to Insects of North America, surely one of the most dog-eared of a collection of dog-eared field guides.

Moving the garden cart in the garage, I noticed something scurrying, which reminded me of a silverfish, but wasn't quite right. It was a Jumping Bristletail, which has been moved from the silverfish (order Thysanura) to the order Microcoryphia. They're forest-floor denizens, and they have a beautiful coppery sheen and three cool-looking tails. To me, they look like something that might have crawled the Permian sea floor. In fact, they appeared in the Devonian period along with the arachnids, and are among the least-changed of all insects. With simple chewing mouthparts, they feed on algae, mosses and lichens.

I particularly like this passage from Wikipedia:

During courtship, the males spin a thread from their abdomen, attach one end to the substrate, and string packages of sperm (spermatophores) along it. After a series of courtship dances, the female picks up the spermatophores and places them on her ovipositor. The female then lays a batch of around 30 eggs in a suitable crevice. The young resemble the adults, and take up to two years to reach sexual maturity. Unlike most insects, the adults continue to moult after reaching adulthood, and typically mate once at each instar. Archaeognaths may have a total lifespan of up to four years, longer than many larger insects.^[2]




What is it about me and odd, long-lived insects? I'm attracted to the primitive, the odd, the venerable. I like knowing that this tiny creature can live up to four years, while much larger and more spectacular insects like the luna moth may croak a week after metamorphosis. (Ah, but the Science Chimp urges that we remember that the luna has had a nice long summer of caterpillar and a winter of pupa under its belt before it takes wing to mate and die).

And now the Science Chimp is warmed up and rubbing her hairy hands in glee. Because late this summer, she finally solved a mystery which has been buggin' her for years. 

See, there are these tiny, tiny insects that flow in packs over the sandstone walls around our patio, over the paving blocks that form our raised garden beds; even over the cemetery headstones at my favorite churchyard.

And nobody I asked knew what they were.

There were difficulties. For one thing, they're very quick, and very difficult to photograph as they race over the stone. Yes, this is a lousy photo, but it's better than the previous 50.

I kept at it, though, and finally got a couple of decent shots of live rockrunners, as I named them (needing to name them something!)
I was elated to discover thin threadlike antennae in this photo, which might help in tracking down an identity. To judge how very tiny this thing is, those are sand grains in the sandstone...

I tried to catch some, hoping to put them in the fridge for awhile and cool them down enough to get some good macro shots. Well, I accidentally killed one in gently clapping my hand over it.

Tiny. Why do I care? Because I have to know what it is, and I don't mind waiting years to find out.

At last, I could see something of its structure.

And though I'd never seen one fly, it had wings! Nice big wings!

 I thumbed through my insect guide. The closest I could get was Springtails, order Collembola. But this thing seemed more insect-like than a springtail. So I hit bugguide.net. I can't remember the series of things I typed into the search box before arriving at Stimulopalpus japonicus. But whoop, there it was.

It's in the Order Psocodea (Barklice, Booklice and Parasitic Lice). It's in the suborder Troctomorpha, and the family  Amphientomidae (Tropical Barklice.) And get this: It was accidentally introduced to the Washington, D.C. area from Japan in the late 1950's and has spread as far west as southern IL to northern AL.

"The introduced population is apparently all-female."

Which means that they're all clones, reproducing through parthenogenesis.

What they're doing in those massive packs, so many that they flow like water over the rock; how they've managed to flourish to such an extent that they're now found on rocks in the middle of tumbling streams and gravestones and my garden walls in Ohio, must remain a mystery. 

At least they have a name for me now. Not that they know or care, these parthenogenic female packs of rockrunners.

Bugs. I can only wonder, and wonder some more, the permanent question mark hovering over my head.