Shape of ant's thorax

Bruce Williams · #1 (**permalink**) 20-12-2009, 12:44 PM

Stony Stratford, Bucks (17th Dec 09).

My pic is not the clearest so please look very carefully at the shape of the thorax in my pic. Now I'm not particularly an ant person so this could easily be the normal shape of an ant's thorax, however I was surprised at the elaborate sculpting and a bit puzzled as to why it's that shape.

Any info on anatomy and/or identification appreciated.

Bruce

Jason Green · #2 (**permalink**) 20-12-2009, 01:12 PM

Hi Bruce,

Not too sure on the species - it looks a little like the standard Lasius niger, but the flash has made it appear a little browner than usual. Anatomy-wise you'll see the thorax and abdomen - but between that is the Propodeum (the bump at the back-end of the thorax), the Petiole (the small link between the thorax and abdomen) and the Node (the small pointed thing above it at the head-end of the abdomen where it joins the propodeum and thorax).

Some genera in the Formicidae family - Myrmica spp. spring to mind - have a further part, a Post-petiole.

They all have fairly elaborate bodies - you see just how multi-jointed they seem when you try and mount one under a microscope!

I hope this is of some help!

Take care,

Jason

JRsbugs · #3 (**permalink**) 20-12-2009, 04:22 PM

Nice shot Bruce. I have pics of one or maybe two ants which look like this, and they don't look at all like Lasius niger to me, much too cute looking.

One thing Ihave noticed, and I may be wrong, is the shape of the back of the head on L. niger is squarish.

One of mine approx. 3mm long was farming aphids which I know L. niger do but it doesn't have the square head shape. The other was about 3mm long and was tending a tiny bug nymph which looked like a piece of tissue paper and can't have been more than 0.5mm long. The interraction between the two was a sight to behold, I should post the pics sometime. Some are understandably not so clear in all parts but it shows the interaction, a difficult job as they constantly moved!

I have been once again on an ant hunt

. There is a list of british species on a pdf I got from this site at the end of the species list, but there's not many species pics there. You will also find more on the anatomy.

Myrm's Ant Nest - Species

Ants are a difficult group, and a frustrating one at that.

You might find some pics of species we have on this site..

Ant Photos - Formicidae Images

Janet

Rossco · #4 (**permalink**) 20-12-2009, 04:36 PM

Bruce

Not sure what species it is as ant's aren't my bag.

As for the thorax shape, however, take a look on the web at some of the tropical species, such as the leaf-cutter ants in the genus Atta. These often have really intricately shaped thoraces. I think the thorax shape is probably a consequence of processes on the inside of the exoskeleton for muscle attachment and selection for defensive structures.

Also, like all insects, the closer you look at them, the more bizarre they appear.

Ross

Bruce Williams · #5 (**permalink**) 20-12-2009, 07:56 PM

Jason, Janet and Ross - Thanks for your help and interest in this posting. It's made me realise that I've been somewhat remiss in overlooking ants as an "interesting" subject. Of course I've read about some of the more exotic species and have taken pics of them (usually concentrating on the head) whenever they've caught my attention - but I've never really taken a close look at them.

Anyway I've spent a couple of hours Googling 'ants' and have had a selective read through my (forgotten) Naturalist Handbook 24 on Ants. I'm not too hot with guide books however I think my ant does look very much like the handbook's illustrations of L. niger and L. fuliginosus.

Janet, thanks for the interesting links. I took quite a few pics of ants farming aphids back in 2006. It took me a while to find the pics this evening (my filing system pre 2008 is non-existent) and I have to say I remember the quality as being rather better than they actually are. So another project for 2010.

Ross - I find insect/arachnid anatomy quite fascinating but sadly relatively poorly documented (on-line anyway). One thing I did read was that the petiole (thanks Jason) provides a flexible junction, enabling the ant to bend its gaster forward to sting or spray its attacker or victim.

Bruce