Seasonal Essay for July

July
One of the delights of childhood on a July evening is catching fireflies (lightning beetles) and placing them temporarily in a jar to watch their amazing tiny flashlights. The intermittent luminescence serves to bring males and females together. There are several species in our area and the rate of flashing varies among them so that only members of the same species will mate. Lightning beetles are beetles (not flies), a group containing at least 300,000 described and named species, roughly a third of all insects. The British biologist, J.B.S. Haldane, was asked by a cleric, "As a biologist, what have you learned about the nature of God?" Haldane replied, "He is inordinately fond of beetles."

Many years ago in New Guinea, a friend and I were collecting biological specimens when in the near distance we saw an intermittent glow. We initially thought that some other crazy biologist was roaming the woods, but when we reached the source it was a tree covered with many hundreds of lightning beetles and they were flashing in unison! It made biological sense. Whereas the light from a single beetle flashing in the dense forest wouldn't carry far, the bright light from many could draw mates from a much larger distance. Synchronous behavior occurs in other animals too. The scattered individual voices of spring peepers (tiny tree frogs) often settle down into synchronous calling.

The organ which produces the light in a lightning beetle is modified muscle, just as is the electric organ of electric eels. The light is efficiently produced, roughly 90% of the energy that goes into the reaction comes out as light. In an incandescent light bulb, the best we can do is 15%, the rest being lost as heat. Fluorescent bulbs are still only about 20% efficient in converting electricity to light, but in comparison with incandescents, for the amount of electricity they do convert, they get much more light.

The next time you push a light switch, think orf those many creatures who come equipped with their own built-in lights.