Sounds of a hot summer afternoon in the country would certainly include the loud, constant, monotonous calls of the cicadas. Cicadas are perhaps the noisiest of all the insects. Actually these penetrating calls are the mating calls of the males; most females are silent. Since the female does not have a hearing organ, scientists think she must receive the sound vibrations of the male’s call. The male cicada makes his call by vibrating a membrane on a kind of sound box located on his thorax, that part of his body between his head and abdomen.
Cicadas live in their adult forms for only one short summer season. During that time they must mate and the female must lay the eggs so that there will be another generation of cicadas. When fall comes, the adults that have somehow managed to escape predators, die. Their young, however, are already in the ground.
After mating, the female hunts for a twig on a tree. Into it she ejects her eggs—often as many as two hundred. Before the end of summer these eggs have hatched and the young nymphs drop to the ground. They burrow into the earth under trees. There they remain for periods of from two to seventeen years, depending on the species. They eat sap from tree roots.
When the cicadas are full grown and it is time for them to emerge, they come to the surface of the ground. Often they build a temporary shelter of mud on top of the ground in which they live for a short while. When they are finally ready to assume adult form, cicadas crawl up a tree trunk or a weed. When they have found a secure place, they rest for a few minutes. Then the top of their old shell begins to split open as the insect expands inside. Once the shell is split all the way from front to back, the insect begins to work its way out. First the head appears, then the centre of the body. It stands upright with only the tip of its back still left in the old shell. Now the emerging insect lets itself fall forward. Hanging on with its legs to the old shell it pulls the back of its body out. At last it is completely free, a colourful ,winged creature. However it still must wait for its wings to expand and dry. Once this has occurred the cicada is an adult, ready for the last phase of its life. The whole emerging process normally takes about an hour.
A heavy rain at the time of emerging is disastrous to the cicada, as are hungry birds and other predators. Some kinds of cicadas emerge in early evening; by the next morning they are flying from tree to tree seeking a mate. There are about fifteen hundred species of cicada in the world. Some, especially those found in the Far East, are quite large, and are used as food by people living in certain regions. For instance, the Borneo cicada is eaten by inhabitants of the Malay Peninsula. This cicada is three inches long and has a wing span of eight inches. One of the most attractive cicadas is the bright red and black blistering cicada of China. The oil cicada of Japan makes a spluttering sound resembling that made by very hot frying oil. One of the most interesting cicadas, because of its long life span, is the periodical or seventeen-year cicada found in the forested areas of North America. In the north the nymphs live underground for about sixteen years and nine months. In the south these cicadas have a thirteen-year life cycle. They do a certain amount of damage to trees by eating the sap from their roots. Cicadas have many enemies. Small mammals eat them, birds eat them and even turtles eat them. As nymphs living underground, they often get fungus diseases. But one of the most unusual enemies of the cicadas is another insect—a wasp called a cicada killer. The female wasp stings the cicada and thus paralyzes it. Then the wasp carries the cicada, although it is larger and much heavier than she is, through the air back to a burrow she has dug in the ground. The wasp lays her egg in this burrow; when the young wasp hatches, it feeds on the captive cicada.
Cicadas Pictures
