No tropical ant is more feared and formidable than the infamous bullet ant (Paraponera clavata)— la hormiga bala. Bullet ants have an extremely tough cuticle, similar to velvet ants (Mutillidae), though more flexible, but still cannot be crushed when squeezed between two fingers… no ant cruelty here, I tested this with a dead ant. They are armed with an especially potent neurotoxic venom that prolongs activation of sodium channels and induces muscle twitching at the site of injection. The sting of Paraponera is among the most unique for hymenopterans in its physiological effects, being primarily pain-inducing but still causing breakdown of red blood cells (hemolysis). Nevertheless, the accumulation of stings from bullet ants appears to be less harmful than those of other colonial ants and wasps, which can have higher levels of cytotoxicity and hemorrhaging.
Bullet ants form subterranean colonies at the base of large trees, often Pentaclethra macroloba. Arboreal nest entrances have also been recorded, but likely serve as a channel through the tree’s interior to the forest floor. Bullet ants are extremely defensive of their nesting sites. Workers can be found guarding the entrance during the day, and when disturbed (scroll down for a video!), they produce stridulations from rasping the abdominal segments against one another and more workers are recruited to join the cacophony. No doubt birds, mammals, and researchers alike are atuned to this distinct sound and avoid the source at all costs. Paraponera primarily forage at night to retrieve nectar and arthropods for the colony, and their routes are more haphazard and less coordinated than smaller ants that deposit trail pheromones more readily. These wandering maneuvers are thought to conserve the production costs for pheromones and may also increase the chances for incidental encounters with prey. Many times I’ve observed empty-handed bullet ants pick up beetles and hemipterans while en route. To my knowledge, there are few natural predators of bullet ants, and the primary sources of mortality come from intercolony conflict, phorid fly parasitoids that oviposit on injured workers, and also Ophiocordyceps fungus.