Edward O. Wilson is best known today as the originator of sociobiology, but his scientific credentials come from his studies of ants. This book, written in collaboration with Bert Hölldobler, a German entomologist, is a popular version of their original scholarly monograph The Ants, published in 1990. Written in a lively style, it contains a wealth of quite fascinating material that is likely to be unknown to most readers. It is abundantly illustrated with photographs and line and colour drawings. It is, in a sense, old-fashioned "natural history", and none the worse for that.
Ants are ancient insects; the earliest ants may well have stung the occasional dinosaur, for primitive ants have been found in amber (fossilized resin) from the middle of the Cretaceous period 90 million years ago. These creatures had anatomical features intermediate between modern ants and wasps. There have been hardly any evolutionary changes in ants for the last 2 million years.
All modern ants are social, although the numbers in their colonies range from a few hundreds to many millions. Their sizes also vary widely, some being very large (especially the queens) while others are barely visible without a magnifying glass. They have quite elaborate brains and are capable of varied although largely stereotypical behaviour, much of which is controlled by chemical signals. But an individual ant is nothing in itself; all its activities are subordinate to the needs of the colony. Hölldobler and Wilson agree with the idea, current for over 100 years now, that the colony can be thought of as a superorganism and that this is not a mere analogy. Just as the cells of the body are specialized to carry out different functions, so with ants: in some species there are wide differences in size, armaments, and behaviour. Particularly among the leafcutters, some workers are tiny, others much larger, and the largest colony members of all, the soldiers, are 300 times heavier than the smaller workers, with heads 6 mm across.
Unlike the termites, all worker ants are female. Historically, this has posed a serious puzzle for evolutionists, including Darwin, since the workers are apparently behaving altruistically in working, and sometimes dying, to preserve the colony. Not until 1963 did the entomologist William D. Hamilton provide a detailed explanation based on the numbers of genes shared by the workers. In essence, this depends on the fact that the sister workers share three-quarters of their genes whereas they share only half their genes with their mother, the queen.
The altruism can sometimes go to quite astonishing degrees. There are even suicide bombers among the ants: workers that literally explode their bodies by muscular contraction in order to spray poison over their enemies. Warfare is in fact endemic among the ants, and is prosecuted with astonishing savagery, sometimes for territorial aggression, sometimes in order to capture slaves. A few species have gone in the opposite direction in an evolutionary sense and have become parasitic on other ants, but this is rare and may not be a successful behaviour in the long term.
Although intended for non-professional readers, the book concludes with a chapter for students and field researchers on basic procedures for collecting ants and for keeping colonies in the laboratory.