Ants: tiny yet powerful
There are more than 12,000 know species of ant and possibly 10,000 more as of yet unknown species. They are all members of the family Formicidae in the order Hymenoptera. They share their order with other insects like wasps (you can see the resemblance if you look hard enough). Over the course of their evolution, these little creatures have become one of the most successful on the entire planet. They have gone from inhabiting one land mass to inhabiting every single landmass with the exception of Antarctica and a few islands (an expansion similar to that of humanities). This astounding success is due, in large part, to their ability to adapt. Ants are social insects, which allows them to work together in colonies to achieve common goals. Even more than that, different ants within a colony can take on specific roles needed for the betterment of the entire group. They have their own form of communication, and they can form symbiotic relationships with almost any living thing, be it another insect or a fungus. Ants are so good at surviving and spreading that it is estimated that they may make up to 25% of the terrestrial animal biomass.
Ants can specialize in a colony, many are foragers. Source
Ants have some very distinctive features. They are the only insect to have elbowed antennae, metapleural glands that produce an antibiotic secretion, and a petiole (look at the picture). They can get between 0.75 and 62 millimeters (0.03-2.0 inches) long, with the largest known living ant being a male driver ant (otherwise known as a "sausage fly"). Ants do not have lungs, instead they absorb oxygen and release carbon dioxide through pores in their exoskeletons. They also don't have a heart as we would think of it. Instead ants have a long tube running along their backs that works to push bodily fluids throughout the their bodies. Much like flies, ants have compound eyes, however, these eyes are good for little more than detecting movement (unless it's a bulldog ant, they have good eyesight). In addition to their primary eyes, most ants also have three small simple eyes (ocelli) on top of their heads that are able to detect light. Due to their poor eyesight, ants rely on their antennae to relay information about their surroundings by picking up both chemical signals and vibrations. Ants communicate using pheromones which are sensed by these antennae. Foraging parties will lay pheromone trails to show each other the most efficient path to nearby food and crushed ants will release pheromones that send nearby ants into a frenzy. This chemical form of communication is used for everything from identifying which colony an individual came from to organizing the division of labor. Ants also do something called haplodiploid sex-determination. It is a fascinating reproduction process where unfertilized eggs will become haploid males and fertilized eggs will become diploid females. The males, called "drones", are there exclusively to mate and eat where the females either become the queen or do the rest of the work necessary for the colony. A queen ant can live up to 30 years, a worker ant can live up to 3 years, and a male ant can only live a few weeks.
Anatomy of a worker ant. Source
Male driver ant (sausage fly). Source
All species of ants form colonies, however these colonies can range in size from around 12 individuals to several million. The smaller colonies tend to be larger, more predatory ants (all ants are technically predatory) that rely on their hunting abilities to catch prey. Large colonies have very high levels of organization, dividing labour in all sorts of crazy ways. The most conventional division of labor goes something like this: new adult ants tend to the queen and care for the young, slightly older ants dig tunnels and the oldest ants go foraging for food and defend the colony. This conventional division isn't the only one, however. Some species of ants will use members of their colony as living food storage devices, gorging them with food. In other species, some ants will be unusually large and strong, these ants will become "soldiers", basically regular worker ants that spend more time defending the colony. The specializations continue, it seems that ants can perform any task required of them, no matter how strange. It was once thought that this specialization was triggered by the environment, but newer research says that it can also be the result of minor differences in genetics.
Honey ants are filled with food to feed others. Source
Ant division of labor is interesting in its own right, but it isn't the only cool thing about ants. Ants are smart, really smart. Usually we think of an ant colony being a raised mound of dirt in the ground, but that isn't always true. One species of ant can cut apart leaves then stitch them together using silk from their larvae to form a home. Other ants can even fashion temporary homes out of their own bodies by holding onto one another. Along that same line, fire ants can work together to form extremely durable rafts for floating on the surface of water. Still other ants can work together to form bridges to cross gaps in the ground or surrounding foliage. There's no limit to what these critters can do!
We usually think of slave holding as being a purely human thing, but it's not. Most ant species fight, raiding each other or trying to take over the other queen's colony. On these raids, they don't just steal food, they also steal the workers and the young. They take their prisoners back to their own colony where the captured ant becomes a slave. That's right, ants have slaves.
Ants aren't just smart, they can learn. Learning is a difficult to prove phenomenon that indicates high levels of adaptability, and isn't found in many insects. Experienced foragers have been observed leading inexperienced foragers out on gathering missions, showing the new ant how to find food. The mentor will slow down if the trainee falls behind and will speed up if the trainee begins to move faster. Other experiments have shown that if an ant is a poor hunter, it will learn that it never finds food and will switch roles, perhaps caring for the young. Likewise, if an ant is an exceptional hunter, it will go foraging more often than other ants. Individuals have the ability to remember past experiences and change their behavior accordingly, it's just fascinating.
Weaver ants stitching together a nest. Source
Ants are wonderful little creatures, capable of working together to find solutions to problems in much the same way a computer would. So, the next time you're about to step on an ant, consider what exactly it is you're stepping on.