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I Bee M

Bumble-Bee Economics

by Bernd Heinrich
Harvard University Press, 245 pp., $17.50

The marvels of the societies of honey bees and their communications by dancing are widely known but probably few people realize that these are only the most sophisticated of the many less developed types of bee communities. There are 20,000 different species with all sorts of different cultures, making up the poorer. Third World of bees. Each species has developed a distinct pattern of organization in the long process of evolution since they first diverged from their carnivorous wasp ancestors when the flowering plants appeared over 100 million years ago.

The bumble bees, also called humble bees, are specially adapted to live in environments of bogs and tundra in temperate regions, where of course there are no flowers for much of the year. Honey bees on the other hand are descended from ancestors living in the tropics where individual trees and shrubs burst into flower at all seasons. As each source of abundant pollen and honey appears a worker honey bee that has found the tree in flower can call all the others to it by her dance on the honeycomb. This is also why honey bees are such useful “commensals”—i.e., organisms with whom association can bring mutual benefits—for human begins who plant crops like fruits and clover that all flower together.

But for the humble bees in the bogs there are no such masses of blooms to be visited. They have evolved a very different strategy whose economics depend upon exploiting the honey and pollen of the scattered flowers that appear throughout the spring and summer. Bernd Heinrich, an entomologist at Berkeley, gives a delightful account of how they do it. As he follows the bees on their foraging he also opens our senses to the sights, sounds, and smells of summer in the country where they live. This is a book about bogs as well as bees, and should appeal to everyone who loves to be in the country, whether he is an entomologist or not.

The bumble bees live in temperate climates and their first problem is survival through the winter. For them there is no cosy hive provided by people, and in fact each colony lasts only for one summer. It ends by producing males and many queens. The latter, after being fertilized by the males, have to weather the winter in a torpid state, buried underground. In the spring a queen that has managed to survive emerges and lays eggs to found a new colony.

At first she has to do all the work herself, gathering honey and pollen to feed the larvae. But she cuts off their supplies before they are fully grown and they become sterile workers who help her by feeding her later progeny. The bumble bees thus pose the question that worries biologists: how can altruistic behavior have evolved? Success in evolution depends upon one’s having some structure or activity that ensures that the next generation contains more creatures like oneself than like others of the species. But here are the sterile workers feeding others, some of whom will ultimately become queens. The answer to the problem is still not fully agreed upon between sociobiologists and others. The bumble bee colony certainly presents remarkable features of combined actions on behalf of the community.

Heinrich describes how their economy is managed by what he calls “decisions over the juggling of costs and benefits.” The bumble bee colony runs on pollen for growth and sugar for energy. These are the resources needed to produce the machinery of the business, which is honeycombs and new workers. The economy must expand as rapidly as possible before the crash at the end of the cycle, and the “profit” is measured as the number of drones and fertilized new queens, to maximize the chance of survival through the winter.

The bees use a multitude of ingenious devices to balance their budget and yield a profit. They are careful conservers of energy. They are cold-blooded insects who can fly only if they are first warmed up by shivering. But this involves expenditure of energy, so there must be no waste. And this, if you will excuse a pun, is the function of the waist. The heat is produced in the muscles of the thorax (the front part) and during warming up there is an ingenious arrangement to keep all the heat there. But heat is used by bumble bees also to warm the nest and incubate the eggs. When the bee is sitting on the eggs to do this, heat is allowed to flow through the narrow waist into the back part. Conversely in flight the abdomen acts like the radiator of a car to keep the bee from overheating.

In the search for flowers that will yield the maximum of pollen and honey the bumble bees use strategies adapted to the conditions. When air temperature is low they visit only flowers that provide enough honey to allow a profit after the energy expenditures necessary to keep warm. Flowers like meadow-sweet yield little honey but are close together, so the bees don’t bother to fly, but walk over them and allow their temperatures to fall. Perhaps the most important factor of all is the time spent in foraging journeys. The bees fly fast (up to twenty kilometers per hour) and spend only about three minutes in the nest between trips. They may make trips of up to five kilometers, but obviously the shorter the better. As Heinrich puts it, the young bees have to learn to be good shoppers, visiting the flowers that give the best yield within a given flying distance. They find the best bargain remarkably quickly with only between two and six trips. Apparently each bumble bee has to learn for itself it is not directed to the most food-rewarding flowers by its nest mates. “So the bumble bee colony relies on individual initiative, whereas the honey bee colony resembles a big corporation that goes after the big markets.”

The beauty of Heinrich’s book is that as you read on he keeps revealing new reasons for being interested in bees. Luckily he is not one of those who believes that we can learn how to manage our society by imitating theirs. After all they have been social animals for a hundred million years, we for only one or two million. Their altruism depends upon special genetic principles which we do not share. All their workers are sterile sisters and their fathers carry only half the number of genes.

But we depend upon bees for more serious matters than advice about sociology. About one third of our food crops are pollinated by bees. The signals that flowers send to the bees that fertilize them provide a whole treatise on the principles of communication. Some orchids have the shape, color, and scent of female bees, tempting the males to copulate with them. “The many messages, each providing a code for a specific species, is undoubtedly an aspect of the variety we perceive as beauty in nature.” Investigating this variety of plant and animal life has led Dr. Heinrich to produce a beautiful book. He ends with drawings of all the plants that he mentions and finally gives a page of sixty colored pictures of the bees themselves.

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