Seasonal Essay for August

I call August the month of the Orthoptera, that order of insects which includes crickets, grasshoppers and katydids, because in August they fill the evening and night air with their calls. These calls serve to bring the sexes together for mating although the cricket's chirp doesn't sound much like a love song to some of us. The Japanese used to keep crickets in cages. They enjoyed their cheery, homey sound, but it also served as an alarm. The footfalls of a nighttime intruder would cause the cricket to stop chirping and the sudden quiet would awaken the sleeping resident.

The snowy tree cricket has a call that is more musical to our ears. Its fairly high tone is difficult to locate, partly because the sound can be focused by its front wings and as the insect turns on its perch, the sound seems to come from different directions. But with patience, searching with a flashlight will disclose the small (3/4 inch), pale green singer. Rate of calling varies with temperature so that if you add 40 to the number of its calls in 15 seconds, you get the approximate temperature in degrees Farenheight.

Many kinds of insects produce sound, but the Orthopterans are especially known for this because the sound is loud and within the range of our hearing. Some produce the sound by rubbing roughened parts of the front wings together. Others rub their hind legs. And of course, making sound has no function if it can't be heard, so they have organs of hearing, located in some species on the abdomen, in others on the front legs, and elsewhere.

Sound making and hearing occur in insects other than Orthopterans. The whine of the wings of a female mosquito is heard through the fluffy antennae of the male. Some animal voices we don't hear at all. The humanly inaudible, high-pitched sound (sonar) of a hunting bat's voice is reflected back to the bat's ears and serves as an echo locator. The sound is also heard by prey moths who take evasive action which fortunately, from the bat's point of view, is not always successful. With a tape recorder you can record some of the animal voices, analyze them by playing back at different speeds, or simply create the chance to enjoy them all year long.