by Matthew Cobb
Take a look at this beautiful insect, photographed by the amazing macro photographer Melvyn Yeo:
If you said it’s been photoshopped, you’re wrong. If you said ‘it looks like a beetle-fly thing’ you’d be right. It is called a beetle fly, and it shows a stunning example of convergent evolution. In beetles, the front pair of wings have evolved to form the beetle’s ‘shell’, and they flip up and separate during flight.
In the Celyphidae, a group of flies found in tropical Africa and in the far East, the scutellum, which is a structure at the rear of the insect’s abdomen THORAX [EMBARRASSING INSECT ANATOMY FAIL] has stretched out to form a hard ‘shell’, just like in a beetle, except that it is solid and does not divide into two. You can see it’s a fly because it still has a fly’s usual front pair of wings, and, just above the ‘knee’ of the middle leg, the reduced rear wing or haltere, which we have discussed three times in the last two weeks!.
Now I said ‘convergent evolution’, but it’s possible they are mimicking beetles (why?). Mind you, if it’s convergent evolution, what solution have the two groups converged on? Are there common selection pressures, and if so what? And if those pressures are so important, why haven’t other groups of flies taken the same route?
Whatever the case, one issue I haven’t been able to resolve is how the flies… fly. I presume the scutellum flips up, but that would create hellish aerodynamics, so maybe they just fly very badly. Any answers out there?
My colleague Richard Preziosi and I were looking at this and Richard hazarded that it’s a gravid female (i.e. she’s looking to lay eggs), and indeed it does almost seem like you can see eggs through the lower part of her abdomen. But a quick image search on Google reveals that lots of the pictured flies (not of the same species) are equally rotund. Here’s another one, from Wikipedia:
Photographer liewwk from Kuala Lumpur has a couple of nice photos including this one:
S/he says about the ecology of this species: ‘Very common in low land jungle with stream/river nearby, size ~3-5mm and very shy to human, not easy to get close normally”
Here’s another picture by Melvyn Yeo:
My favourite fly book, Stephen Marshall’s Flies, says on page 359:
“Known beetle fly larvae … feed on decaying grass or skeletonizing the upper surfaces of dead leaves. Beetle flies are usual found in wet areas, often among grasses near bodies of water. Most of the 120 or so species in this small family are Oriental, several species occur in Africa, some range as far north as Afghanistan and nepal, and others are found southeast to new Guinea and the Solomon Islands. These attractive insects are relatively well known despite their mostly tropical range.’
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These guys are just plain cool.
Prof
I found the following on another Web Site: It seems to indiate a gear-like mechanism in flagella!!?
As a small tease, if you choose to spend a few minutes watching you will learn that the propulsion system is tied to a complex neural network allowing for movement along a chemical gradient, each motor can turn 100,000 rpm, yet reverse within a quarter turn, proton drive is the power source, and this is the only freely rotating structure known in nature (complete a bearings and seals!)
The comparison to an electric outboard motor is inescapable, and makes the man made model look very crude and inefficient.
Aww, come on man! Give us link!
They really are so fly!
The beetles they appear to imitate are Chrysomelidae – leaf beetles – like this one
http://tinyurl.com/nzv5bu2
Which still leaves us wondering why they have converged? Why would a fly get an advantage looking like a gravid beetle?!
Are there any examples of beetles converging on flies?
OK, so it’s a beetle fly – it’s still not a croco-duck.
Morphology Fails….
the scutellum, which is a structure at the rear of the insect’s abdomen, …
The scutellum is part of the thorax!
DUH. Fixed. Apologies to all.
It looks to me like the wings emerge from the sides of the scutellum, thereby avoiding the need to move it out of the way.
That’s what it looked like to me, as well. It would have been nice–well, not “nice” but useful, perhaps–if the photographer could have startled the fly a bit to make it take off, and try to get some images of flight.
Just one minor quibble: should it not read “…scutellum, which is a structure at the rear of the insect’s THORAX…”?
A very interesting read nonetheless, thanks for bringing this to everyone’s attention!
– James
It looks like the attachment point for the wings is in front of the scutellum, so there’s no mystery.
I was thinking the same. Perhaps the wing first moves to the side to clear the stretched scutellum.
If you google-image “celyphidae” you can see several pics of pinned specimens with wings out.
Yes indeed. Thanks.
For anyone curious here are two links direct to images of beetle flies with their wings deployed.
Beetle Fly 1
Beetle Fly 2
What we really need though is super slo-mo video of a live one flying.
Normally i spray them and i am scared of them and that the beetle will bite me and it may sting some of them are poisonous and handle it and can spray poison . i wack them and kill it .
Beetles? They may scare you – that’s your mind – but I don’t think that any can BITE you. Unless my insect anatomy is completely bugged up, one of the defining characteristics of a beetle is the presence of mouth parts modified from the basic insect plan to be able to pierce into plant stems and suck the juices.
I’ll concede that such a mechanism might be modified into sucking through skin, but I’m not aware of specific examples. One of the bug-lovers on board will know better for sure, but I don’t think you need worry about being bitten by a beetle.
Similar comment for beetles being poisonous. If it bites you and you die, then I don’t think it was a beetle.
The things scare and upset me too – and I’m back off to tropical Africa next week – but I do try to contain my fear and revulsion and resist the temptation to swat them. Plus, of course, loading the bloodstream up with Malarone. (Anti-malarial drug.)
No, beetles have biting mouthparts. From Wikipedia:
There are many you wouldn’t want to be bit by! (Even the new (imported for insect control, I believe) Asian ladybugs bite!)
You may be thinking of the Hemiptera, which have sucking mouthparts usually used to feed on plants (leafhoppers, aphids, etc.); but they include spp you’d want to avoid as well–bedbugs and kissing bugs, for instance.
Ah well, thats why I look at rocks rather than fossils. Too much like stamp collecting, even with evolution for a framework.
If you spray them you are no friend of the natural world.
i whack them and too away .
i whack them and hoo them.
i don’t like beetles and i find them very creppy.
This is not a beetle…
Don’t beetles do the same? I doubt they beat their cover wings as much as those evolved for propelling them, if at all. Actually I thought those were held fixed.
Generally, small winged animals (or plants) fly in a regime where viscosity is predominant. The closest analogy would be swimming, recognizing that there some species rely on buoyancy as well.
Lots of swimmers are less streamlined. Fast swimmers are generally streamlined AFAIK. And the same seems to go for insects (body drooping and broad bumble bees vs sleek and straight dragon flies, say).
But I haven’t seen a thorough description of “small world” aerodynamics yet.
And with “predominant” I meant dominant.
I think the suggested difference in aerodynamics would be that beetle elytra, being composed of two “halves,” could split open and sort of rotate out of the way of the thus released wings, while this singular structure would have to simply lift up. But as has been noted, this fly’s wings can emerge without the hardened scutellem having to move at all.
Scutellum, of course.
I’ve wondered about that. The elytra seem like a very poor design from the point of view of aerodynamics. As you mention, aerodynamics goes a little funky at the scales involved. One would presume, at least, that having some rapidly beating wings that close to big obstructions would create some weird vortices. Perhaps the elytra are why beetles tend to be rather clumsy fliers.
The wing-folding mechanism beetles (or at least most of them?) have is also something it’d be interesting to see explained. Little papery things that are presumably subject to all kinds of stress, yet have hinges in them. Presumably it works but, like the elytra, it just seems like a bad idea.
“poor design” – watch your language – the point is there IS no design!
Of course there’s design. Just no deity doing the designing.
I was going to suggest it was an interesting case of mimicry b/c the top fly resembled chrysomelid beetles that taste bad. But the other species shown are not obviously advertising that they taste bad, so now I am not sure about that idea. The enlarged scutellum could still be used to protect the wings, as the elytra do in beetles. So convergent evolution for wing protection is still on the table.
Great post and outstanding photos!
There’s a whole family, or possibly a subfamily if your taste runs that way, of true bugs called shield bugs, in which the enlarged scutellum forms a shield over the back. There, the scutellum is fixed and the wings just pop out to the side. I suspect the same holds true for these flies.
Yes, a very clear example for convergent evolution. «Stink bugs» tend to have triangular flattened shapes and these flies are rotund, but _Megacopta cribraria_ (a serious agricultural pest) is reminiscent of these guys even in that regard.
To quote Huxley: ‘How incredibly stupid (of me) not to have thought of that!’
There are coleoptera that are similar, in that they have fused elytra. Their hind wings also pop out to the side for flight.
Reblogged this on Mark Solock Blog.
Since we’re mentioning halteres again, does anyone know how the (original) Olympian long jumpers used them yet? I know that people have been trying to figure out what they did with them for decades, but I don’t recall anyone actually coming up with a solution.
One assumes that they lead to some sort of advantage, and so when they’re figured out, they’ll be banned to much sporting hooplah. But I’ve not heard that hooplah, so I deduce that no-one knows, yet.
This Nat Geo article from 2010 claims that the problem has been solved. Some interesting items from the article.
Regarding an advantage in the modern long jump.
The long jump in the ancient games was a standing long jump.
Thanks ; I’ll have a look at that.
I was wandering through a museum in Athens, head fried by the heat, and remember glancing at a vase, thinking “Halteres!”, then spending 10 minutes trying to remember what they were, contrary to my brain’s free association speed.