ASU-Ask A Biologist - Ant Anatomy

Imagine being the size of an ant. Be careful - a face-to-face encounter with an ant would be scary and potentially life-threatening! But, if you avoided being eaten, you could learn a lot about ant anatomy from a close-up view. Ants have many body parts that are normally hard to see without a magnifying glass or microscope. And each structure has its own special function.

When you come across an ant on the ground, it’s almost always a worker ant. Workers are adult females that don’t reproduce, but perform all the other jobs needed to keep an ant colony alive and healthy. In case you are wondering, there are no male workers in ant colonies. What do these female worker ants look like? Let’s take a closer look.

Now that you can see how ants are put together and what each part is named, let’s learn what each part does and what is inside of them.

The ant’s second body segment, the mesosoma, is packed full with muscles that power its three pairs of legs. The legs are designed for running – ants can run very fast for their size. At the end of each leg is a hooked claw that is used to climb and hang on to things.

The gaster contains the ant’s heart, digestive system, and chemical weaponry. Some ants have a sting, which is used to inject venom into enemies. Others have a tiny opening at the tip of their gaster through which they spray acid to stun prey or defend themselves.

In between the mesosoma and the gaster is the petiole (and in some ants, the post-petiole). This is one body part that distinguishes ants from other insects. The petiole (and post-petiole, when present) provides a flexible junction, allowing the ant to bend its gaster forward to sting or spray.

Finally, the entire body of an ant is covered by a hard exoskeleton that provides support, protection, and a barrier against water loss.

You may have noticed we didn’t talk about ant heads. Like you and me, ants use their heads to sense information about the world around them. This is very important for their survival and the life of the colony. If you watch an ant’s head, the antennae are always moving back and forth, touching, tasting, and smelling everything within reach. Each antenna is bent in the middle like the elbow of a human arm – this is another unique feature of ants.

Their compound eyes, like the eyes of most insects, can contain hundreds of lenses that combine to form a single image in the ant’s brain. Ants that use vision to hunt for prey have big compound eyes. Other ants that live in dark places have reduced eyes and may even be blind. Some ants also have three simple eyes called ocelli that detect light.

The mandibles are an ant’s most important tool. Ants don’t have grasping forelegs, so they use their mandibles like human hands to hold and carry things. Mandibles can also be used for biting, crushing, cutting, digging, fighting, and hunting. Hidden by the mandibles is the mouth, which ants use not only to eat, but also to clean themselves and nestmates.

Ant heads, especially the eyes and mandibles, come in all shapes and sizes and provide clues to the kinds of food ants eat and the different lifestyles they live.

Worker ants perform all sorts of jobs for their colony. In most species, all workers are roughly the same size. However, some ants have different sizes of workers that serve different roles. Minor workers are smaller and perform general labor such as taking care of the young, building and cleaning the nest, and gathering food. Major workers are larger and specialized to perform certain tasks. For example, major workers called soldiers have large heads and powerful mandibles used to guard and defend the colony.

Queen ants spend most of their lives inside the nest laying eggs, but you may see one outside during the mating season. Queens have most of the same body parts as workers. However, queens are usually much bigger than workers. The queen’s large gaster contains her reproductive system. Queens also start out with wings, but these are torn off after mating. More muscles are required in the mesosoma to power flight.

The only time you’ll encounter a male ant is during mating, because they die shortly afterward. Like queens, males have wings and muscular mesosomas for flying. But males are typically not as large as queens and have smaller heads with bigger eyes and straighter antennae.

Head, thorax, and abdomen?... Like other insects, ants do have a head, thorax, and abdomen, but the thorax and abdomen are not obvious... The ant’s mesosoma includes the thorax plus the front of the abdomen – they are fused together. The rest of the abdomen is divided into the petiole, post-petiole (when present), and gaster.

Ouch! An ant bit me! ... People are usually mistaken when they think it’s the bite of ant that hurts. Most of the ants we encounter are too small to inflict pain with their bites. However, even some of the tiniest ants can inject venom through their stings, causing burning, itching, and/or swelling. It’s the sting, not the bite, that earns them names like "fire ant" and "bullet ant."

Ants, like all living things, have an individual life cycle. However, because ants are social – they live in family groups that cooperate to build nests, find food, and raise offspring - they also have a colony life cycle. Ant colonies range in size from just a few individuals to millions! The social lifestyle of ants is a major reason for their success.

These are just few questions that we have answered in our ant facts section that you can read.

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