There has been of late a lot of discussion of the cicada emergence and the their noisy mating calls. Despite the fervor surrounding the cacophonous insect's emergence this year — in which thousands of adult cicadas will noisily arise to mate after a 17-year subterranean maturation period — Princeton's balmy days and nights should be relatively free of this noise. That is because there are several types of cicadas that emerge at different times and Princeton is not on the list this year. Male cicadas have loud noisemakers called tymbals on the sides of the abdominal base. Their "singing" is not the stridulation (where one structure is rubbed against another) of many other familiar sound-producing insects like crickets: the tymbals are regions of the exoskeleton that are modified to form a complex membrane with thin, membranous portions and thickened ribs.
Brood X, the Great Eastern Brood, is one of 15 broods of periodical cicadas that appear regularly throughout the eastern United States. It has the greatest range and concentration of any of the 17-year cicadas. One of its home fields is Princeton. NJ.
Every 17 years, cicadas tunnel en mass to the surface of the ground, lay eggs, and then die off in several weeks. The combination of long dormancy, simultaneous emergence of vast numbers, and short period before the nymphs' burrowing underground to safety, allows the brood to survive even massive predation.
Adult cicadas are alive for only a few weeks after a disproportionately long grub life spent underground gorging on nutritious tree water, Horn said. Periodical cicadas spend their youth — which for humans is roughly the time between birth and graduating middle or high school — moving further underground to feed on the thickest, juiciest tree roots.
As these nymphs approach adulthood, they burrow toward the surface to emerge more or less in unison once the soil temperature is more than 63 degrees Fahrenheit. In northern states such as New Jersey this occurs around early June. The nymphs then find a leaf on which to perch and undergo their transformation into winged adults.
Brood X's most recent appearance was in the spring and early summer of 2004 throughout an area roughly enclosed by Illinois, Michigan, New York and Georgia. The next appearances will be in 2021 and 2038.
Most of the North American species are in the genus Tibicen: the annual or jar fly or dog-day cicadas (so named because they emerge in late July and August). The best-known North American genus is Magicicada, however. These periodical cicadas have an extremely long life cycle of 13 to 17 years and emerge in large numbers. Another American species is the Apache cicada, Diceroprocta apache.
Australian cicadas differ from many other types because of that continent's diversity of climate and terrain. In Australia, cicadas are found on tropical islands and cold coastal beaches around Tasmania; in tropical wetlands; high and low deserts; alpine areas of New South Wales and Victoria; large cities like Sydney, Melbourne, and Brisbane; and Tasmanian highlands and snowfields.
So there are many different types of cicadas as well as a very large amount of them. Why so many?
Cicadas are commonly eaten by birds, and sometimes by squirrels. Another known predator is the cicada killer wasp.
Some species of cicada also have an unusual defense mechanism to protect themselves from predation, known as predator satiation: because so many emerge at once, the number of cicadas in any given area exceeds the amount predators can eat; all available predators are thus satiated, and the remaining cicadas can breed in peace.
For further information see Brood X.
Adult Cicada image via Wikipedia.