National Geographic : 1966 Dec
so important to soil formation, erosion pre vention, or colorful bloom depends on insects for reproduction. Insects appeared on earth probably 350 million years ago. In the eons since, they have developed remarkable adaptations to plants - involved interdependence of one on the other. And hard-to-believe oddities: Pupae of common butterflies that may winter on low shrubbery with no covering but ice and snow. Fruit flies that in flight beat their wings 13,000 strokes a minute. Aphids that give birth only to live female offspring-daughters who, even before they are born, already have begun to develop within themselves the embryos of a third generation. Odd Partnerships Link Two Worlds Vast, complex, and exciting, the insect realm pulsates about the blooms of forest, hill, and plain. Most of the insect traffic comes there for nectar. The insects gather it as a source of quick energy for themselves, or as a nutritious addition to food for larval young. Nectar averages from 30 to 40 percent pure sugar; in apple blossoms, it may contain as much as 87 percent. To gather nectar, insects have perfected remarkable adaptations. Mouth parts have developed into strawlike proboscises, often longer than the insects' bodies, that poke deep into flowers. Alimentary tracts have developed honey stomachs, or crops, that become carrying pouches and storage vats; the tiny honey ant may swell to eight times normal weight and hang like a balloon in underground chambers.* But adaptation hasn't been all on the side of the insects. Plants have changed too. Spe cies which cannot depend on chance winds to spread their pollen have developed lures that encourage the crawlers and fliers, whose visits help the transfer from one blossom to another. In addition to nectar, flowers attract with color, odor, landing-platform petals, and dot tings and markings that serve as guides point ing out the nectar cup. This mutual adaptation has become so in terwoven that some plants cater only to cer tain insects, whose lives in turn hinge exclu sively on that plant. The black bees of my sleepless night, for example, time their short flying existence to the blossoming period of the evening primrose. Other andrenas emerge from their wintering stage when the willow catkins burst into bloom. And in California one year, unseasonable weather caused some spring flowers to blossom in the fall; simul taneously, certain spring bees appeared at the flowers. *See "Living Honey Jars of the Ant World," by Ross E. Hutchins, NATIONAL GEOGRAPHIC, March, 1962. Author and photographer: Dr. J. W. MacSwain (right), Professor of Entomology at the University of California at Berkeley, has gained unusual distinction both for his broad knowledge of insects and as a specialist on certain bees and beetles. A veteran of insect-collecting expe ditions, he recently flew to Iran to study alfalfa pollination. Dr. Edward S. Ross, whose re markable photographs accompany Dr. MacSwain's article, is Curator of Entomology at the California Academy of Sciences in San Fran cisco. He works only inches from his subjects, hand-holding both camera and flash lamp, since he often has but moments to focus the lens and snap the shutter after encountering an insect. As youngsters, both scientists were enthusiastic insect collectors. Later they went to college together in California.