Review of "The Leafcutter Ants" by Bert Hölldobler and Edward O. Wilson, W.W. Norton & Co., 160 pp.
By Mark J. Palmer
International Marine Mammal Project
Earth Island Institute
One of nature's fascinating spectacles, at least on the small spectacle side of things, is a line of leafcutter ants, marching off across a trail (or via a glass tube in insectariums) with leaf upon leaf flashing green.
Bert Hölldobler and E.O. Wilson, authorities on ants, tell the story of leafcutter ants in detail, and the story of this line of troopers in the woods becomes an epic indeed. The subhead of their book is "Civilization by Instinct." Leafcutter ants, it turns out, build elaborate nests that stretch for many meters underground, with chamber upon chamber dedicated to a form of insect agriculture.
The leafy bits these ants carefully cut out are destined to be laid down and "farmed" as a growing bed for fungus, which the ants eat. The complexity of this process is mind-boggling, but occurs without the intelligence we ascribe to such activity in "higher" animals and humans.
"The Leafcutter Ants" is thoroughly researched and well documented (so much so that the references tend to get in the way of the reading), suitable for general reading and expert reference alike. Hölldobler and Wilson received a Pulitzer Prize for their extensive book "The Ants" -
"The Leafcutter Ants" is essentially chapters from that larger work. Also confusing is the wealth of Latin names to describe the behavior and life of different species of the leafcutter ants, found in both the New World and the Old World tropics and subtropics, so it can get a bit difficult to remember each genus that is referenced.
The book works through all aspects of the biology and behavior of leafcutter ants. Some species have more advanced organization than others. For example, one species not only has the worker ants that cut and move the leafs into the nest, but includes smaller "fighter" ants which ride piggyback on the worker to fend off attacks of parasitic flies that prey on the workers. The range of complexity in the organization of the different species and genera of leafcutter ants illustrates the evolution of such complexity and adaptations over time.
The center of the nest is the bloated queen ant, which lays the eggs that provide the colony with workers. Farmed fungi provides the colony with food. The ants even secrete antibiotics to control invading fungi in the farm cells that threaten the food source.
Then there are the predatory ants that try to steal the fungus from leafcutter ant colonies. These specialized freebooters will invade a nest, take it over, eat all the leftover ant pupae and fungus, and then move on to invade another ant nest. Others are more sneaky, living as parasites within the leafcutter ant colony itself.
The ants communicate chemically, such as marking trails to leaf sources from the nest, and using sound, such as rubbing body parts to produce sound (called stridulation, a word I really like), which appears to be picked by other ants from the ground rather than through the air.
The authors conclude: "...(T)here can be little doubt that the gigantic colonies of the Atta leafcutters, with their interlocking symbiont communities and extreme complexity and mechanisms of cohesiveness, deserve special attention as the greatest superorganisms on Earth discovered to the present time."
The "discovered at the present time" qualifier is important. E.O. Wilson has pointed out that our knowledge of the insects inhabiting the soil is extremely limited. New species are being discovered all the time, and their interactions, while critical to the functioning of natural ecosystems, are barely understood. There is a lot to be learned from looking down into all that dirt.
The book includes excellent black & white photographs and diagrams that illustrate the text, and a handy glossary of ant terms.
"The Leafcutter Ants" is an excellent and detailed introduction to a species that builds incredible civilizations beneath our feet. Highly recommended.