Males are up to 14 mm (0.55 in) and have black heads and thoraxes, and dark reddish-brown gasters and limbs.

[5] This ant occurs in lowland tropical rainforests in South America where its range extends from Panama and Venezuela to Peru, Bolivia, Paraguay, Uruguay and northern Argentina.

It is a common arboreal species and colonies are found in forested areas, parkland with isolated trees, and urban habitats.

In one instance, a troop of army ants Nomamyrmex esenbeckii was seen attacking a colony, and the C. atratus workers made a living wall to defend the entrance, aligning their heavily sclerotised heads to prevent the army ants from getting inside to attack their brood.

The ants bring infected bird faeces back to the colony to feed to their young.