Bullet ant, Paraponera clavata, Jatun Sacha reserve, Ecuador.

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The most infamous ant in the world is surely the tropical American bullet ant, Paraponera clavata. This conspicuous insect is known for an unusually painful sting. It is not the only big rainforest ant, however, and other species are frequently mistaken for it.

Here is how to make sure that big ant you saw was really a bullet ant.

1. Check your location: in the wild, bullet ants are only found in low-elevation forests from Honduras south to Paraguay. If you are not in Central or South America, you don’t have a bullet ant. (source)

2. Check the size: bullet ants are not just large, they are massive – over an inch long. They look like plastic toy ants brought to life.

3. Check for the characteristic thoracic horns. Bullet ants have a pair of blunt horns on the first segment of the thorax. No other ant its size has the horns.

4. Check the shape of the petiolar node. The waist of the bullet ant has a sharp, forward-leaning triangular node.

With these criteria in mind, here is a real bullet ant:

South America? Check. Massive? Check. Horns? Check. Forward-pointing waist segment? Check.

For comparison, these other large South American species are not bullet ants:

Dinoponera is big- even a bit bigger than the bullet ant, but Dinoponera is darker in color and lacks the horns on the thorax.

Ectatomma tuberculatum is an ubiquitous big rainforest ant with a shape confusingly similar to that of the bullet ant. But Ectatomma is too small, as are the horns, and the waist segment is the wrong shape.

Pachycondyla villosa is common and also packs a painful sting, but this large species is not big enough to be a bullet ant and it lacks the horns.

Atta leafcutter ant soldiers are big and even have the thoracic horns, but they aren’t big enough, they lack the right waist shape, and are their overall body proportions are different.

Cephalotes atratus black turtle ants are common and conspicuous, but they are much smaller than bullet ants and have sharp spines rather than blunt horns.

The golden carpenter ant Camponotus sericeiventris is not quite big enough, its horns are more forward on the thorax, and it doesn’t have the right waist shape.

 With any luck, you should now be able to check the identification of your purported bullet ant without having to run a sting test.