What on earth has that crane fly done, I asked myself? It had flown up from some grasses beside a stream as I walked past, and landed back in the shade of a tree beside the trail I was following. It hung from a leaf but was too far in to approach closely. My binoculars, meant for birding, were a help, but without ones designed for close in work, only gave me a distant look, better than naked eye, but still not enough for real detail. The same held for the small screen on my camera. But I could make out enough to show me that this bug had done something odd.
Crane flies are those critters that look like huge mosquitoes. Fortunately for us, they do not bite—they’d draw a pint of blood if they did. Actually most of them don’t even feed as adults. They’ve done all the growing they need to do in the grub stage. After pupating, they mate, lay eggs for the next generation and die. Of course, there are thousands of crane fly species, so some do all kinds of crazy things, but what this one had done looked unplanned. There was a pale thing on a hind foot, perhaps the molted skin of a leaf hopper. Had the crane fly accidentally stepped into it and been unable to shake it loose? It seemed unlikely. Most insects are quite fastidious, and this one was making no effort to rid itself of the excrescence. I would have to wait to see the full photo images on my computer to find out.
Up the image came, and things got even weirder than they already were. The pale thing was not a skin, but a living plant bug of some sort, and it was being gripped by the crane fly’s hind foot. No accident this! And those two wings? I’d never seen a fly’s wing with a pterostigma, the often-colorful, thickened spot near the wingtip of, for example, a dragonfly. And those crazy wing veins, more like a fisherman’s net than the flies’ wings I knew. Then, zooming in to look at its head, I could see this one was eating an ant. No way!
But it was. So perhaps this was some kind of robber fly. It didn’t look much like the ones I’d seen, but at least robber flies are predators. Off to the books and BugGuide.net I went, but none of the robber flies, nor any of the other fly families I looked at fit the image I had. Still, with well over 100,000 species described so far, and probably even more than that waiting classification, a fly like this could turn up.
I had two usable images. I had glanced at both, but been concentrating my attention on the first. When I shifted, I found in the second, almost completely hidden, the pterostigma of a third wing. The penny dropped. This thing had four wings, not two! The second pair was merely out of view behind the wee monster’s body. It was not a fly at all!
This time my look through the books paid off. My “crane fly” was actually a member of the order Mecoptera, the scorpionflies, which are neither scorpions nor flies, but they are definitely predaceous. Mine belonged to a group called the hanging flies, an appropriate term since that was exactly what my critter was doing. They also have an interesting mating behavior that explained the plant bug this one was holding. Scorpionflies use their hind legs to capture prey, normally the small insects that make up their diet. But a male may also offer a prey item to a female as an inducement to mate. She gets to eat, he gets to procreate. And I got to learn a little more about this weird, amazing world we live in.