Cicadas, whose steady hum fills the late summer air,are more often heard then seen. Males make the sharp sound with plate-like organs on the thorax. Some species are called harvestflies because of their late summer appearance; others are called 13-year and 17-year locusts, though the 75 species of cicadas differ widely in the time they take to mature. The females cut slits in young twigs and deposit eggs in them. This sometimes causes damage in nurseries and orchards because the slit twigs break easily in the wind. As the wingless, scaly young hatch, they drop to the ground, burrow in, and stay there 4 to 20 years (depending on the species and the latitude) as nymphs living on juices sucked from roots. The full-grown nymph climbs a tree trunk. The skin splits down the back; the adult emerges. In most species, adults ordinarily live a few weeks - long enough to mate and lay eggs. "Broods" or large colonies of periodical (13- and 17- year) cicadas emerge en masse, and many are eaten by birds.
