Caste systems

Caste systems in ant societies

The ant colony consists of several different groups. The dominant of course is the workers, amounting to millions of individuals in some species. There’s also the queen, the center of the colony, and lastly the males.

Ants are usually divided into three castes: reproductive females, reproductive males, and non-reproductive females. This translates to queens, males, and workers.

The ants have a very efficient colony system where individual ants are born into their role – their caste. In many species, the queen is huge and would never be able to work for the colony, while the workers do not have the required fallopian tubes to lay millions of eggs. The males could actually help out with the colony chores, but mostly they do not. The bodies of the ants are specially built for their tasks, and even though ants are known to be very adaptable, some castes are not. Roughly put: the workers are there to work, the queen to lay eggs and the males are for flying away and mating with new queens. But what differentiates the castes from one another, anatomically and in behavior?

Three different castes in ant societies

Queen

While some ant species only have one queen (monogyne) there are species whose colonies might consist of several (polygyne).

The queen is the focal point of the colony. All the work being done is to make sure her egg-laying can go on. She is the mother of all the workers and is protected to the teeth by her children. Though from an evolutionary perspective, this isn’t an act of love – rather a way of maximizing the possible spreading of their genes. Because the workers do not lay any eggs of their own, the queen becomes the most important ant in the colony.

Ant queens are born with large wings. These are accompanied by a large thorax, a result of the large wing muscles being located there. When mated and about to found her colony, she bites off her wings (or rather snaps them off with her legs), simply because she won’t need them anymore. The queens also have a big elastic abdomen which will grow with the rate of her egg-laying. It is made out of four to five segments, connected by a thin but stretchable material. To begin with, the segments lay side by side, touching each other, but are with time separated more and more. (1)

It might seem like a classy thing, being the queen and all. But the fact is that she is only there for one thing: laying eggs. There is no rule connected to her status as a queen, it is simply something we’ve created to understand the structure of their societies.

Males

Much like the queens, males have large wings and larger bodies than the worker ants. The difference in body type from the queen is that the males’ abdomens are quite slender. They also have flaps underneath belonging to their sexual organs. These are always visible even though they might be hard for us to spot.

The males are born in the nest and after birth start wandering around it. Most of the time, they do not perform any of the colony duties but rather bide their time waiting for the nuptial flights. Their mission in life is not to contribute to the colony, but to mate with as many females as possible. When the big day comes the males die off within the hour after mating. If they’re lucky they can survive for a few days. But unfortunately, in the ant world, there is no life for a male ant after mating. By then, the females are either dead or beneath the ground, founding their new colonies. The males can not survive another year in the hopes of a new generation of females taking flight. (2)

Males are almost always darkly colored, independent of other castes' color schemes. This makes it very difficult to tell their species because many males look the same. (3)

Workers

The colony hero, the worker, is the winner by numbers. During the course of evolution, they’ve sacrificed their ability to spawn their own offspring. This has made their ovaries tiny.

The ant workers carry no sets of wings. They are born in the colony and never have to travel vast distances to remote locations. Their job is to tend to the queen, the eggs, larvae, and pupae, dig tunnels and chambers, and expand and secure the nest. They collect food, moisture, and materials to protect the colony from predators and parasites. Their caste name is well deserved.

Size-wise the workers usually differ a lot from each other when comparing species, but most have in common that they are smaller than the queens and males. Workers may also come in different sizes even though they’re the same species. Some have enormous heads whilst others are thin and agile. The ones blessed with strength use it to crack open seeds and defend the nest and are commonly known as soldiers. (4) Their heads can sometimes be as big as the rest of their bodies.

Most workers can lay eggs, but since they are unmated they can only produce males. To produce a female, ants need seed from a male.

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References

1. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln “Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 31 (Swedish)

2. Bert Holldobler & Edward O. Wilson (1995) “Journey to the ants” p. 30

3. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln “Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 32 (Swedish)

4. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln “Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 31-32 (Swedish)