An Atta laevigata soldier advances on the photographer. These giant ants are specialized for nest defense, and their bite easily draws blood. Carrancas, Minas Gerais, Brazil

Myrmecologist Ricardo ("Bob") Solar ponders the sharp mandibles of an Atta laevigata soldier, the world's largest leafcutter ant. Carrancas, Minas Gerais, Brazil

Atta laevigata is the largest of the leafcutter ants. Carrancas, Minas Gerais, Brazil

Colobopsis etiolata

Worker dimorphism in the cork-headed ant Colobopsis etiolata. Gonzales, Texas, USA.

Colobopsis etiolata

The light color and strongly margined clypeal "plug" distinguish Colobopsis etiolata from other Texan Colobopsis. Gonzales, Texas, USA.

Camponotus (Colobopsis) impressus major worker. The blunt head serves as a living door to this species' twig nests. Laboratory colony at the University of Central Florida, USA

Colobopsis impressa

Colobopsis impressa major worker. Laboratory colony at the University of Central Florida, USA

Colobopsis impressa

Colobopsis impressa major worker. The blunt head serves as a living door to this species' twig nests. Laboratory colony at the University of Central Florida, USA

Dorylus driver ants are quick to defend their colonies. Here, a soldier bites down on an intruding myrmecologist. This behavior has been co-opted by traditional medicine in some cultures to make sutures of ant heads. Kibale forest, Uganda

A Dorylus driver ant soldier stands guard over a foraging column. Kibale Forest, Uganda

Dorylus driver ants are quick to defend their colonies. Here, a soldier bites down on an intruding myrmecologist. Kibale forest, Uganda

Eciton burchellii army ant soldier. The hooked mandibles are used to protect army ant colonies against vertebrate predators. Maquipucuna Reserve, Pichincha, Ecuador

An Eciton hamatum soldier uses her ice-tong mandibles to latch on to the photographer's skin. This gives her the leverage to use her stinger (at the read end of the animal) and makes her very difficult to remove. Jatun Sacha reserve, Napo, Ecuador

An Eciton burchellii soldier brandishes her hooked mandibles. These unwieldy weapons are designed to grab vertebrate predators and deter them from stealing the army ants' own catch. Jatun Sacha reserve, Napo, Ecuador

Camponotus rufipes is among the most common ant species in parts of South America. Curitiba, Paraná, Brazil

Portrait of a Camponotus sericeiventris soldier, one of the most recognizable ants in Central and South America. This species is a tree-dwelling insect that, remarkably, can glide back to a trunk when dislodged, steering with her flattened, aerodynamic legs. Carrancas, Minas Gerais, Brazil

Camponotus tortuganus, major worker Archbold Biological Station, Florida, USA

Camponotus atriceps major worker Coclé, Panama

Camponotus ulcerosus major worker, showing the enlarged head she uses for plugging the nest entrance. Sierra Vista, Arizona, USA

Camponotus ulcerosus, major and minor workers Sierra Vista, Arizona, USA

Atta colombica soldier. Captive colony at the University of Texas

Major and minor workers of Atta cephalotes demonstrating the size extremes among worker ants in a single leafcutter ant colony. Captive colony at the University of Illinois

Atta cephalotes, close-up of the head of a soldier. The sharp mandibles of this ant can easily slice through skin, so handle these ants with care! Captive colony at the California Academy of Sciences

Soldier and worker ants in the fungus garden of an Atta cephalotes colony. Captive colony at the California Academy of Sciences