The spring of 1991 is one that many Asheville residents will remember primarily because of the mass emergence of hundreds, no thousands, no MILLIONS it seemed of large black bugs with bright red eyes that seemed to be everywhere! Commonly called the 17- year locust, these insects are not really locusts at all. Their proper name is the Periodical Cicada.

Cicadas are the largest North American members of the insect order Homoptera which includes aphids, plant hoppers, and scale insects. They are common insects that many of us hear but seldom see in the summertime. The loud buzzing "whirr" that we hear high in the trees during hot summer days is made by these insects.

There are several species of cicadas. All have interesting life cycles that may span two to five years or in the case of the periodical cicada, 13 or 17 years depending on the locality. There are many different "broods" or populations of cicadas in specific areas but these generally overlap each other in range so that there are always some adults present in the summertime in most areas.

Surprisingly however, there are only 14 broods of the 17-year cicada and 5 of the 13-year cicada known to exist today. Some of these broods are quite extensive and occupy large areas of the country while others are comparatively much smaller, covering less than 100 square miles. Because of the simultaneous mass emergence of the periodical cicada over such extensive land areas it is no wonder that this insect commands our attention.

The immature form of the cicada is known as a nymph. Wingless cicada nymphs live underground feeding on the roots of perennial plants, primarily trees. When they mature, the nymphs burrow to the surface and climb up on plant stems, tree trunks, or any other available vertical support where they firmly attach themselves with their claws. The skin of the nymph then splits down the back and the winged adult cicada emerges. Adult cicadas usually live only a few weeks, just long enough to find mates and reproduce.

Much of the male cicada' s large abdomen is composed of two hollow chambers. Powerful muscles cause membranes in the abdomen to vibrate and the chambers act as resonators to amplify the sound. The intensity of one male cicada buzzing is quite impressive, the sound produced by a brood of many thousands of the periodical cicada can be quite nerve wracking as we recently experienced! However the incessant buzzing attracts the female cicada and mating takes place soon afterwards.

Cicadas are often thought to cause feeding damage to plants but this is not generally true. The only real damage done by cicadas is when the female lays her eggs. Female cicadas use a knife-like ovipositor in their abdomen to cut slits in the tender outer twigs of trees. They then deposit their eggs inside these slits. This often causes the twigs to wither and die but usually does little overall damage to the large, mature hardwood trees that the cicadas seem to prefer. After a few weeks, young cicada nymphs hatch and fall to the ground where they burrow out of sight until they too will one day emerge to complete the cycle.

You might wonder why all the periodical cicadas in an area emerge at once in such great numbers. It is thought that this is a survival strategy. Cicadas are preyed upon by many animals. By overwhelming the predators in a given area with large numbers of prey, the majority will live long enough to reproduce their kind. Also interesting is the egg-laying and subsequent withering and dying of the tender, young branch tips. Is this nature's way of pruning the forest? But most amazing of all is the cicada's timing. How do they know when to surface after living underground for many years?

Only certain areas around Asheville were "fortunate" enough to play host to the periodical cicada while others will have to wait their turn. Many people viewed the event as something horrible while those of us who appreciate the natural order of things found it to be extremely fascinating and the culmination of a marvelous plan. Personally, I can't wait for the next great cicada invasion. I've got it marked on my 2008 calendar.