A Tale of a Mushroom and Two Beetles

[I recently posted about slugs eating mushrooms. This is episode two, so to speak, of a series about a mushroom benefiting other species.]

Two Blue-winged Rove Beetles, Philonthus caeruleipennis, were crawling around on the cap of a wine-dark russula mushroom.

Like all 68,000 species of Rove Beetles, their electric-blue wing covers are tiny, leaving most of their body exposed.

The body is jointed and was often curled up like the one on the right::

It looked as though they were eating the mushroom:

except that the chewed up flesh was left lying there, apparently not swallowed. They disappeared periodically into a hole they had excavated in the mushroom.

I took lots of photos, then came home and did some reading. Most Rove Beetles are predators, not mushroom-fanciers. Some do create brood dens by digging out a cavity for their young, but not this species. It seemed they must be hunting, but the beetles are only 0.5″ long, and their prey will perforce be smaller still, and hard to see. Finally, though, I realized that one of my photos contained proof: the beetle below has caught a tiny insect in its jaws.

Apparently being only 1/2″ long does not preclude being a hunter, so long as your prey is even smaller. As Shakespeare said, “Though she be but little, she is fierce. “

PS I do not know what insect had been caught by this Rove Beetle, but a variety of small insects feed on mushrooms as they age. Here are two 0.2″ Pitch-black Collared Ants,  Aphaenogaster picea, feeding on a different decaying mushroom:

and a Slender Springtail, Lepidocyrtus paradoxus, 0.06″ long, which was sharing a Russula mushroom with a slug:

And smallest of all, these tiny flies, about .04″ long, fruit-fly sized, on a decaying red mushroom.