E-mail A Friend Tell a friend about the information found on this page by sending them an e-mail.   Your Name: Your E-mail:   Type an e-mail address, then click add: Add a Personal Message: (Optional)

March/April 2000 issue	In this issue Table of Contents Editor’s Notebook Inside Story Feature: Raccoons Curious by nature

OVER THE CENTURIES, the humble ant has often been held up as a model for humans to follow. "Go to the ant," King Solomon advised. "Consider her ways and be wise." Solomon drew approving attention to the ant’s prudent labours, as she busily stocked her larder for summer and winter. But the ant’s chief claim to fame throughout history has been her reputation for selfless service. A worker ant has often been described as a kind of six-legged Mother Teresa, tirelessly devoted to the good of her fellows in the anthill. Lacking the ability to produce young of her own, a worker gives herself over to serving her mother, the queen, usually the only one in the colony fully capable of reproducing. As she grows older, she may embark on perilous excursions away from the nest to find food, which she loyally carries back to feed her queen and her co-workers. If the colony falls under attack by predators or enemy ants, she may even give her life in its defence.

But this picture of self-sacrifice has been badly tarnished by recent revelations. Beneath the apparent altruism of ant society, it now seems, there lurks a potential for mutiny and violence.

Take, for example, the wood ant, Formica exsecta. (Although F. exsecta lives only in Europe, a number of similar, mound-building Formica ants occur in Canada.) As in most species, wood ant workers normally feed and care for larvae produced by their mother. But as Finnish biologist Liselotte Sundstrom and her Swiss colleagues, Michel Chapuisat and Laurent Keller, have recently observed, those tender nursemaids can suddenly turn into infant-murderers. Without warning, the workers may begin to kill hundreds of male larvae by biting them, in what amounts to a mass execution of their own brothers.

Under the best of circumstances, the life of a male ant is bleak. Even if he survives to maturity, he enjoys only one brief moment of glory. He is a "reproductive," and his sole function is to leave the ant hill on a nuptial flight, mate with a young queen from another colony and promptly die. But his sperm will live after him in the body of the young queen, who will use it to produce eggs for her new colony. His span may be short but his influence is lasting.

So why would worker ants suddenly rise in revolt and prevent their brothers from fulfilling this role? The reason for their twisted behaviour appears to lie in the twisted strands of their DNA. An ant colony is literally one big family, composed, for the most part, of a queen-mother and her teeming masses of worker-daughters. Each of the workers carries two sets of chromosomes, one from her mother and one from her father. Because the queen ant also has two sets of genes, she bequeaths half of her genetic material, on average, to each of the workers. But ant "kings" differ from queens — and from most of the animal world — in having only one set of chromosomes. Since this is all they have to offer to their offspring, it becomes the common inheritance of their daughters. So each worker receives about half of her mother’s chromosomes and all of her father’s.

This unusual situation means that sister ants, the workers, are extremely close relatives, since any given pair will share about three-quarters of their genetic material. Among humans, by contrast, siblings usually only have about half of their genes in common. In fact, worker ants from the same colony are more closely related to one another than we humans are to our own sons or daughters.

An anthill is therefore a sister act on a grand scale. Worker ants co-operate in raising their younger sisters (the female larvae in the queen’s current brood) because it is an effective way to ensure that their own genes will survive into the future. By serving one another, they serve themselves. But workers have much less in common with brothers than they do with sisters. Since a male larva has only one set of chromosomes — half from each parent — he will only share about a quarter of his genetic material with each of his sisters. The workers are therefore closer kin to female larvae than they are to the males, and this helps to explain why they may decide to eliminate their brothers. Genetically, it is not in their best interests to care for them. To add insult to injury, the workers apparently feed the bodies of their victims to their favourites, the surviving female larvae. (Presumably the murderous workers distinguish between the sexes by "tasting" them with their antennae, since that is the way ants communicate with one another.)

This coup represents a triumph of the workers over the queen. Since the queen is equally related to her male and female offspring, she has an interest in the survival of all her progeny. But because she is totally specialized as an egg-laying machine — scarcely able to move — she has no way of disciplining the mutineers. Chalk one up for the workers!

From the time of King Solomon on, people have often seen in ants what they wanted to see in one another: co-operative, productive behaviour. But our new understanding suggests that ants have very little to teach us about being human. Instead, they can remind us of the ingenuity of natural selection, which counts both ants and ourselves among its most fascinating inventions.

Candace Savage is a Saskatoon-based author of 18 books on wildlife, environmental issues and other subjects.

top