The natural time sense
1. One of the most amazing of living things, the honeybee, has recently been shown to possess still another remarkable skill. It has a built-in alarm clock that goes off exactly every 24 hours.
2. Scientists have long known that bees carry a sort of wrist watch inside their bodies. They will return to the same spot, day after day, right to the minute, to feed on sugar-water left for them. To find out how the bees manage to tell time, an unusual experiment was carried out four years ago. Two young German biologists in Paris trained bees to come out for sugar-water every day at exactly 8:15 p.m. The scientists then set out to baffle the bees. When it is 8:15 p.m. in Paris, New York City's Eastern Day-light Saving time is only 3:15 p.m. If the hive were flown to New York between feedings, which time would the bees follow-Paris' or New York's?
3. So, immediately after a night feeding in Paris, the hive was sealed and rushed off on an air liner. In New York, scientists from the American Museum of National History placed the hive in a specially prepared laboratory in the museum. At exactly 3:15 p.m. New York time - a precise 24 hours after having been fed in Paris - the bees swarmed out of their hive. The experiment proved conclusively that in spite of a 3,500-mile flight and differences in local time, the bees' alarm clocks rang right on their 24-hour schedule.
4. As further proof, the experiment was repeated-only this time the same hive of bees had its alarm set in New York and was flown to Paris. There, too. They emerged from their hive exactly 24 hours later for their accustomed feeding.
5. Scientists now believe that many, if not all, living things are born with some type of hidden clock. These clocks are sometimes set by the number of hours of light or darkness in a day, by the rhythm of the tides or by the seasons.
6. One of the most remarkable of nature's living clocks belongs to the fiddler crab, that familiar beach-dweller with the overgrown claw. Biologists have long known that the crab's shell is darkest during the day, grows pale in late afternoon, then begins to darken again at daybreak. This daytime darkening is valuable for protection against enemies and sunlight, and for many years it was thought to be a simple response by the crab to the sun-just as if we were to get a tan during the day and lose it at night.
7. But when an enterprising scientist placed a fiddler crab in darkness, he was amazed to find that the color of the crab's shell kept ticking off the time with the same accuracy.
8. Yet another startling fact was revealed: the crab's shell reached the darkest color about 50 minutes later each day. There was a second clock inside the crab, for the tides also occur 50 minutes later from day to day. Moreover, even when the crabs were taken from the beach and put back in the dark, they continued their tidal rhythm. More research disclosed that a crab from Cape Cod, Massachusetts, reached its darkest color four hours earlier than the one taken from a beach on a neighboring island. The tides on the nearby island were found to be exactly four hours later than the Cape Cod tides.
9. Ants don't carry calendars around with them any more than fiddler crabs possess real wrist watches. But ants show amazing accuracy as to the day of the year. Each year, an ant nest sends out winged, young queens on mating flights. Hundreds of them may fly out of a single nest in the soil. Last summer, at the crest of my mountain, I watched an ant city prepare to send forth its young queens. At the precise moment that they took wing, a colony of the same species that my wife was watching near the bottom of the mountain, also sent its queen on a wedding flight. There was, of course, no way could the two colonies have checked take-off time with each other.
10. Entomologist Albro T.Gaul once jotted down in his notebook that a particular species of ant in northern Massachusetts began its wedding flight at a certain day and time. He later learned that another entomologist in New Jersey, 260 miles away, observed a wedding flight by the same species of ant, on the same day, and at exactly the same time! This split-second timing is not always the rule. However, most flights take place within a definite period of time.
11. Birds also have built-in timepieces which send them off on fall and spring migrations. What the birds really have is a clock-like mechanism which allows them to time hours of darkness or light in each day.
12. But what sends birds northward again in the spring? New research by Dr. Albert Wolfson of Northwestern University seems to indicate that the timing of return flight is extraordinarily complex. In the fall of the year the short days and long nights cause the "clocks" in migratory birds to undergo a kind of "winding" in preparation for their spring return and breeding. Then during the late fall and winter as the clock "ticks", certain physiological changes occur in the bird. The length of each day during the winter determines how fast the clock will run, and hence when the "alarm" will ring for the spring migration. The clock continues to run through breeding time, then stops-to be re-wound again the next fall.
13. Scientists are now learning that many of the clocks of nature can be reset, speeded up or slowed down-all for our benefit. Pioneering experiments at the U.S. Department of Agriculture's research center in Beltsville, Maryland, have shown that plants can be helped to develop faster in less time. By increasing or lessening the hours of darkness in each day, the scientists have been able to turn plant growth off and on like an electric switch.
14. New knowledge about nature's living clocks has practical applications. For man, too, seems to follow daily rhythms. The amount of sugar in our blood stream varies with the time of day, as does our temperature. More of the cells in our skin and muscles divide during the night hours than during the day. By tinkering with the clocks of plants and animals, scientists may learn more about the fascinating way our bodies work.