FEBRUARY
2004

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

02-12-04

Legislators Debate Daylight-Saving Time: Can Spring be Far Behind?

Every year about this time, the Indiana General Assembly engages in a debate about the merits of daylight-saving time. The idea of saving daylight is somewhat curious. I'm not sure how you would go about saving daylight. We do produce light, thanks to electricity. But the amount of sunlight is beyond our control. The best we can do is "work while the sun shines."

That was not a problem in the early days of humankind. Early humans hunted and gathered when it was light and went to sleep when it was dark. For many years, farmers adhered to the adage of working from "sunrise to sunset." Scientists refer to animals that are active during daylight as diurnal.

Humans are, by nature, diurnal animals. We are also social creatures who generally work and play in groups. To make it easier to plan all that group stuff, we came up with a system for keeping time. Part of the time system was keyed to the dark and light cycle associated with the Earth's spin. One spin was divided into 24 parts called hours. Now, we could get together at the same time during the light to do a job or just socialize.

The system worked fine, if the interaction was just among people in a local area. We could start work at 8 a.m., work an 8-hour day and quit at 5 p.m., being in the light all the while. However, everyone in a large area couldn't start work at the same time and still start in the light. Folks further west would be in the dark, even if the clock read the same. So we created time zones and roughly keyed the time with the sun. It worked great!

But, wait a minute. During the summer months, the amount of sunlight increases so, if we start working at 8 a.m., there is a lot of sunlight wasted before we go to work. Enter daylight-saving time. Just move that magic 8 a.m. hour up an hour so that 8 a.m. is really 7 a.m. That way, we have more hours of daylight after work. We have saved some daylight. Not really, but there are more hours of daylight after school or factory closing time. That gives us more daylight hours for things other than work.

Many insects are also diurnal with their activity keyed to daylight hours. But since insects are cold-blooded, they cannot survive cold temperatures. Unlike humans, they can't turn their clocks backward or forward when the days get longer or shorter. However, the insects do monitor the hours of daylight in order to plan for good and bad times-mostly for bad times.

As the days get shorter in the fall, insects to begin to prepare for winter. Some, like wooly bear caterpillars, start looking for a place to curl up and spend the winter. Others, like ladybird beetles and boxelder bugs, fly in search of sites to hibernate. Still others, like many aphids, fly to winter host plants to lay eggs, which will not hatch until spring.

Honey bees also use day length to orchestrate their activities. For instance, at this very time, honey bee colonies are raising temperatures within the hive to nearly 90 F, in order to incubate the eggs soon to be oviposited by the queen. Why are they doing this now in what is often the coldest part of the winter? Because it is necessary for the colony to have a lot of new bees in the spring when the flowers begin to blossom and produce nectar. It takes about six weeks for new bees to emerge.

How do the bees know it's time to start brood rearing? It is keyed into day length. As the days get longer, it's is a sure sign that spring is on its way. The longer days don't mean warmer days at first. In fact, my father often repeated the old saw, "As the winter days get longer the cold gets stronger!" But as all of nature knows, the length of the day is the only consistent thing from year to year. And the bees don't worry about daylight-saving time.

 

Writer: Tom Turpin
Editor: Olivia Maddox