A cosmopolitan friend of mine named Jim Shuman has traveled extensively to observe natural history phenomena, and he claims that no place he has been--including an African jungle--is noisier than the summer woods of South Carolina's Piedmont.

Camping out with me near Hilton Pond at York, Shuman was astounded at the nightly symphony of croaking toads, squeaking bats, whip-poor-wills, bellowing bullfrogs, chattering flying squirrels, hooting owls, melodious mockingbirds, and--loudest of all--the ceaseless accusations of the katydids.

Our nights are indeed noisy, but so are our days, especially as summer finally winds down toward fall. It is then we hear another sound that always impresses my friend Shuman: the incessant buzz of the cicada.

Cicadas (pronounced "sick-kay-duh") are rather large insects, averaging slightly more than two inches long, but they make far more noise than their size might indicate.

Although about 75 cicada species live in eastern North America, most are tree dwellers we hear but don't see. Many people are familiar with the juveniles, or at least their artifacts; those translucent, hollow, brown "bug shells" found on twigs and tree trunks are exoskeletons of the final nymph stage. Little boys startle little girls by displaying these "shells" nonchalantly on collars and shirtsleeves; my mother tells me that, back when I was an imp, I showed up at Sunday School with one on the tip of my nose.

The cicada nymphs that shed those skins lived several years in the ground before emerging. Adults breed in the summer--the pulsating buzz of the male is his mating call--and the female lays eggs in a twig that usually withers and falls to earth. Eggs hatch and miniscule nymphs migrate into the soil, where they dine year-round on root juice.

All cicadas and their relatives (including leaf hoppers, aphids, and scale insects) have long, narrow mouthparts that they plunge, hypodermic-like, into plant parts. The immature cicadas burrow around, absorbing sugars from roots of perennial plants and molting into ever larger nymphal stages. Their sap-sucking habits probably have little effect on mature trees and shrubs; deaths of saplings and nursery stock usually come from destruction of twigs when adult females lay eggs. Whether these nymphal root parasites will have a detrimental effect this year on our drought-weakened trees may be yet another story.

There are two main types of cicadas. One group, the "periodical cicadas," has adults with reddish eyes and wing veins. These are among the commonest of the cicadas, and they go through diverse and well-documented life cycles. Entomologists--scientists who study insects--have determined that lives of North American periodical cicadas are exceptionally lengthy, hence the names "13-year" and "17-year" cicadas.

Dr. Donald J. Borror, author of a classic entomology textbook, reports there are probably 13 different broods of 17-year cicadas, and five of 13-year cicadas. The broods emerge in different years and have different geographic ranges, with the longer-lived species being mostly northern. To complicate matters further, there are three species of 17-year cicadas, and three species of 13-year cicadas. What all this means is a given summer's population of periodical cicadas may contain adults of up to six species who hatched from eggs either 13 or 17 years ago and who spent an amazingly long time in the soil.

In some years periodical cicadas are more prolific, and some species reproduce in larger numbers than others, such that sometimes there are huge numbers of emerging adults while in other years there are none at all. Since there appear to be occasional population explosions, cicadas--which some people erroneously call "locusts"--actually may have been responsible for some historical insect plagues.

Having shared all this information with you, I must reveal that cicadas you have heard lately may not be "periodical cicadas" after all. We certainly have this type in the Piedmont, and in some years there are many half-inch round holes in lawns and bare soil where their nymphs have emerged. Most years, however, the commonest cicadas in this area are of a second group known as "dog-day cicadas" (see top photo).

How aptly-named are these insects that serenade us on sultry evenings during the Dog Days of August. Their loud, pulsating calls seem to come from every tree, as indeed they may. The male makes this "noise" (read "music" if you are a nature-lover) from a pair of tymbals on top of his abdomen. These structures, each covered by a bright white flap in dog-day cicadas, contain ribbed membranes that bend rapidly back and forth as the insect breathes. The process is analagous to those Halloween noisemakers called "crickets," and the resultant clicks--which resonate in the cicada's nearly-hollow abdomen--are produced so rapidly that human ears hear only a flat buzz.

The songs of some cicadas actually attract males of the same species. As individual males gather at a communal song site, their concentrated chorus is much louder, making it easier for a female to find her potential mate.

Different cicada species buzz at different pulses and frequencies, from different heights, or at different times of the day. Entomologist Borror, known also for his splendid recordings of bird songs, claims the astute listener can distinguish cicada species not only by quality, location, and time of song, but also by a distinctive "disturbance squawk or 'protest' sound" made when handled or disturbed. From this I conclude his ears must be far better than mine.

York County's "dog-day cicadas," with their large squarish heads, huge dark popeyes, long membranous wings, and mottled green back markings, have life cycles that are poorly understood. The shortest known cycle--egg to adult--lasts for at least four years, but nobody knows for sure how long nymphs of local species stay in the ground.

What IS known is that even if they have long life cycles, their broods do overlap so that some emerge each year. Thus, here in the Piedmont we are always guaranteed our summer choir of dog-day cicadas to remind us of mixed blessings:

--August is nearly over,

--school is about to start,

--and it's bound to get cooler any day now.