
above a cicada nymph, note the front legs adapted for digging
Adult males can make a very loud noise when they
vibrate membranes in a pair of organs, called tymbals, on their lower abdomen. They do this to attract a mate. This is called stridulation. the noise can be heard up to 1 km away.
After mating the female lays her eggs in twigs. The eggs hatch and the nymphs drop to the ground and dig into the soil. This is where they will spend most of their life sucking sap from roots. The length of time spent as a nymph depends on the species, but it is usually a prime number, e.g. 7, 13, 17. In North America the 17 year cicada is Magicicada septendecim, and the 13 year is Magicicada cassisii or cassini.
On the left is a photograph sent to me by a visitor to the site. It shows an adult cicada emerging from the exoskeleton of its final nymph stage. At the end of the final nymph stage it digs out of the soil to reach the surface. When the adult emerges the wings and outer surfaces are soft and crumpled. Blood pumped through the wings veins will expand the wings to their full extent, and the air will dry and harden the adult exoskeleton. As it dries the final colouration of the insect will emerge.