Two pavement ant colonies fight for territory along the shores of Clinton Lake, Illinois.

Even the most epic moments of ant warfare can seem inconspicuous from the towering height of our human eyes. The fisherman above, for instance, didn’t even flinch at the hostilities at his feet, even after I pointed out the boiling mass of angry ants. “Someone must’ve spilled something there,” he grunted as he moved on.

But nothing was spilled. This was a territorial boundary between two large colonies of Tetramorium pavement ants. I happened across it while hiking along the shores of Clinton Lake last week, just in time to watch the ants’ numbers escalate along the front. Both colonies were pouring all their fighting-age workers into the fray, hoping to push the borders back and claim a larger swath of prime lakeside real estate.

Granted, from six feet up pavement ants don’t look like much:

But drop down to their level and the battle takes on a different appearance:

Pavement ant fights are one of the great insect spectacles of the northern hemisphere. These Eurasian ants were introduced to North America over 100 years ago and have naturalized across the continent. Where colonies meet, they sort out their space via conspicuously massive battles. Since pavement ants are common in urban areas, the contests frequently play out on city sidewalks. As in this video.

You’d think that colonies wouldn’t be able to sustain the carnage of continuous battle involving most of their worker force. But the ants are far cleverer than that.

The remarkable thing is that relatively few participants receive serious injury. There is all sorts of shoving and biting and pulling about, of course, but these ants rarely use the full force of their weaponry. Rather, the individuals seem to fight with just enough gusto to test the strength of the opposing colony. It’s a show of numbers rather than one-on-one skill.  The stronger colony is able to push the front backward, advancing their territory, but not pushing so hard that the effort costs them valuable workers.

In this afternoon’s Battle for Clinton Lake, the uphill colony had the upper hand. The front inched slowly towards the lake, assuring that the larger colony would control the larger territory.

Incidentally, that lovely three-leaved plant overshadowing the contested territory is poison ivy. I had a moment that tested my dedication as a photographer: do I lie down in the ivy for the money shot of the fisherman and the ants?

Of course I did, and now I’ve got a souvenir rash on my arm. These are the sacrifices we here at Myrmecos make for you readers.


photo details:
(1 & 2)Canon EOS 7d with Canon 17-40mm f/4.0 L wide-angle zoom lens
(1)ISO 200  F/13, 1/125 sec, handheld 550EX  strobe
(2)ISO 200  F/6.3, 1/125 sec, handheld 550EX  strobe
(3 & 4) Canon EOS 7d camera with Canon MP-E 65mm 1-5x macro lens
ISO 100 f/13 1/250 sec, diffused twin flash