Harry’s advent calendar of insects day 5: Poecilobothrus nobilitatus

It’s tempting to just concentrate on the showiest insect families — butterflies, moths, beetles, dragonflies — at the expense of the incredible variety of flies, bugs, fleas, ants, termites, cockroaches and so on.

But let’s have at least one fly. There are lots of things with ‘fly’ in the name — butterfly, caddisfly, scorpionfly and so on — but the true flies, the diptera, are the ones with just one pair of wings: house flies, bluebottles, mosquitoes, gnats, midges, craneflies, horse flies, hoverflies and so on.

This particular fly is Poecilobothrus nobilitatus.

You can see that it’s a bit prettier than some fly species, but it’s not exactly a showstopper.

So why I have I picked it for my advent calendar? Because it dances.

This video was taken at my garden pond, in June, three years ago (I think it’s the right species!). Look particularly in the top right corner.

You can see a couple of males flashing their wings towards a female. OK, it’s not the most dramatic courtship display in nature, it doesn’t compare to birds of paradise or capercaillies; but still, it’s a neat thing to find in a suburban garden, all these little flies earnestly lekking on the lily pads.

» Langbeinfliege Poecilobothrus nobilitatus 110615 005.jpg is © Jürgen Mangelsdorf and used under a CC by-nc-nd licence.

Dancing flies

Flies doing a little mating dance on our lily pads. I think they might be a species called Poecilobothrus nobilitatus, but that’s a provisional ID for the moment. Sorry for the camera-shake.

Some local insects

Earlier in the season, most of the damselflies were blue ones; now they’re all blue-tailed:

This bit of south London is, slightly unexpectedly, a stronghold for the increasingly rare stag beetle. At this time of year you tend to see them flying overhead in the evening; but the weather has been so miserable that I haven’t really been outside much in the evenings. I did see one crawling across the pavement a couple of days ago, though. This, however, is not that species; it’s the more common lesser stag beetle, which is not nearly as big, and even the males don’t have antlers.

This is a hoverfly. Like most hoverflies, it’s a wasp mimic; they nearly all have black and yellow stripes, but they don’t sting. This is more spectacular than most, though; the large size and brownish colour are its attempt to look like a hornet. I think it does quite a good job, although looking at it closely like this it’s obviously a species of fly. We don’t actually have any hornets around here—I’m not sure I’ve ever seen one in the UK, although they do live here—so I don’t know how effective the mimicry is.

And here’s a holly blue. You can see the abdomen curled around on the ivy; presumably it’s laying eggs. It’s lives on the holly and the ivy, which is very Christmassy of it.

Flies, again.

A little while back I was talking about the extraordinary number of insect species just within the UK, and I said:

What I find staggering about these numbers is that it implies there are so many different evolutionary niches available for such apparently similar creatures. Even the 51 species of mayfly are slightly mind-boggling, but how can there possibly be 6900 different ways of successfully being a fly?

Well, there are 6900 separate answers to that question, but here’s just one (typical?) example. They’re found a new species of fly in Scotland. “The tiny black Christii fly measures just 2mm long and lives under the bark of dead aspen trees.” But not, presumably, living aspen trees. Or dead willow trees.

Although I guess that just begs the question “what is so specialised about their behaviour that they can only live in such a narrowly-defined habitat?”

Close Menu