Cicada. Close-up of an adult cicada camouflaged against the bark of a tree. Cicadas are best known for their rhythmic mating calls,which fill the air in warm countries. The sound is produced by an oscillating membrane in an abdominal cavity. The semi-rigid,arched membrane,or tymbal,is pulled out of shape by specialised muscles to produce a loud "click". The membrane flicks back and forth,producing 120-600 clicks per second. Cicadas spend all but a month of their lives underground,where the nymph feeds on the sap of tree roots. The nymphs of each species emerge at the same time,then molt,feed,mate and die |