The Ant-Mugging Flies of Kwazulu-Natal

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A Crematogaster ant is held up by a kleptoparasitic Milichia patrizii ant-mugging fly.

Last July, while wandering about the coastal forests of St. Lucia in eastern South Africa, I happened across an intriguing scene half-way up a spiny Acacia trunk. Some diminutive gray flies were pestering a trail of ants as they walked along the tree.

The flies' exact activities were hard to observe with the naked eye, but it looked like nothing I'd ever seen. They seemed to be grabbing ants, pinning them to the trunk, and after a few seconds letting them go again.

The macro lens on my camera serves as a handy field microscope. Conveniently, the flies were so focused on attacking the ants I could place the lens nearly on top of them and observe the details of their activities without spooking them. On inspection, it turned out that the flies were stealing food.

Later, I sent my photos to milichiid expert Irina Brake. She identified the perpetrators as Milichia patrizii, a species whose behavior had not been previously recorded. So we wrote up a short article in African Invertebrates that came out today. As the paper is behind a subscription barrier I'll share a few of the photos here.

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Stalking the victims.


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The flies stop the ants by grasping the ants' antennae between their own. According to Irina, this use of antennae to subdue other insects is entirely new for flies.


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The fly triggers an automatic regurgitation response by tapping the ant's palps with her proboscis. Oddly enough, once the ant has acquiesced the fly releases her victim's antenna and the ant just sits there. There may be a chemical communication going on between the tip of the ants antennae and the concave upper lip of the fly, but we don't know. Might be a project of interest to a South African student. If any are reading this. Hint, hint, hint.


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The ants leave themselves open to kleptoparasitism by having a highly stereotyped food exchange behavior. Here, two of the Crematogaster demonstrate how it is supposed to be done. The flies have apparently figured out how to game the ants' own communication system.


Source: Wild, A.L. & Brake, I. 2009. Field observations on Milichia patrizii ant-mugging flies (Diptera: Milichiidae: Milichiinae) in KwaZulu-Natal, South Africa. African Invertebrates 50 (1): 205-212.

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Fascinating. Amazing shots too, I like the iridescence displayed on the flies' wings.

Wow. Just -- wow!

By Julie Stahlhut (not verified) on 04 May 2009 #permalink

I am (very probably) heading to South Africa in about 11 weeks. Up till today, I had never even thought twice about a macro lens for the trip... now I am thinking about auctioning off a kidney on ebay to get one. Got anything used you want to sell? Nikon?

Didn't think so.

Very very cool pics. And congrats on the discovery!

Very very cool. And amazing photos!

Fantastic photographs, as usual.

I spent half and hour on my hands and knees yesterday, trying to photograph ants in my backyard, with little success. Maybe I could import some of these flies to hold them down for me?

thats a fantastic one. cool pics indeed.

Wow, that is so amazing.

By liudvikas (not verified) on 04 May 2009 #permalink

Wow, that is so amazing.

By liudvikas (not verified) on 04 May 2009 #permalink

Wow, that is so amazing.

By liudvikas (not verified) on 04 May 2009 #permalink

Wow, that is so amazing.

By liudvikas (not verified) on 04 May 2009 #permalink

Im speechless....And here i was thinking humans were the only life form capable of such!!

Truly incredible! Thank you so much for sharing this!

Phindile's speechlessness makes up for liudvikas's logorrhea, I suppose.

My own comment was already reflected by Adrian. How do you do it?!

By James C. Trager (not verified) on 05 May 2009 #permalink

The words I would have used are already taken, so I'll make up WowMazing! Fascinating behaviour, fascinating basis for it and stunning photos. Not only are the bugs beautifully portrayed but even the bark is gorgeous.

Is that bark typical of the type of tree?

By Mike from Ottawa (not verified) on 05 May 2009 #permalink

Well done! This will definitely be included in lessons on animal behvior in my AP Biology class, you shall be acknowledged of course!!

Does anyone have any information on subscribing to the publication African Invertbrates? I tried to send a request and my e-mail was returned.

What lens did you use and what camera? love the pics. great story.

Tal

really cool, and always interesting to see what bloggers are publishing.

Good reminder tha humans aren't the only ones on this planet who have learned how to hack... wow

I love it when ordinary observation in the field nets a discovery for a sharp-eyed person who cares to look. Good for you! It's especially nice that this is brand new.

Fascinating and well recorded. I seem to remember reading, some years ago, about a mosquito, in SE Asia I think, of the genus Harpagomyia that does something similar, only it actually inserts its proboscis into the ant's crop, again the ant is a Crematogaster species. It would be nice to know of other occurences of flies, or other insects taking advantage of ants in this sort of way, or to know if other genera of ants are similarly effected.

Interesting!

It would be nice to know of other occurences of flies, or other insects taking advantage of ants in this sort of way, or to know if other genera of ants are similarly effected.

Good would be nice to know of other occurences of flies, or other insects taking advantage of ants in this sort of way, or to know if other genera of ants are similarly effected.

Good would be nice to know of other occurences of flies, or other insects taking advantage of ants in this sort of way, or to know if other genera of ants are similarly effected.

Harpagomyia that does something similar, only it actually inserts its proboscis into the ant's crop, again the ant is a Crematogaster species. It would be nice to know of other occurences of flies

Fascinating and well recorded. I seem to remember reading, some years ago, about a mosquito, in SE Asia I think, of the genus Harpagomyia that does something similar, only it actually inserts its proboscis into the ant's crop, again the ant is a Crematogaster species. It would be nice to know of other occurences of flies, or other insects taking advantage of ants in this sort of way, or to know if other genera of ants are similarly effected

The words I would have used are already taken, so I'll make up WowMazing! Fascinating behaviour, fascinating basis for it and stunning photos. Not only are the bugs beautifully portrayed but even the bark is gorgeous.

Is that bark typical of the type of tree