Leafcutters are one of the most striking ants I’ve encountered, with their giant spiky bodies and stilt legs. Unlike most other ants, leafcutters no longer retain the ability to sting or spray venom. These ants are specialized for doing what their name implies–cutting leaves–and this can be seen clearly in the powerfully-jawed major workers. In fact, the jaws latch on so strongly, staying clenched even after death, that beheaded workers are sometimes used to close wounds. While in Argentina, my labmate Paul tried this out on a papercut. Cure possibly less pleasant than the ailment. Very effective, though.
In my occasional encounters with leafcutters of the genus Atta, I was particularly impressed by the truly gigantic, sweeping nests a single colony can make. Although not particularly tall, these mounds can cover a lot of ground, littered with cast off plant material and abuzz with busily working ants. Apparently the 10-15 foot mounds I’ve seen don’t even come brush the upper limits: Wikipedia says the central mound can grow to more than 100 feet across.
I’ve hardly ever encountered leafcutters in my area of Texas, but there is one large colony of Texas leafcutter ants (Atta texana) deep inside our local Lick Creek Park if you know where to look.