CICADIDAE 573 



a chirp somewhat like that of a cricket and a very loud, shrill 

 screech prolonged for fifteen or twenty seconds, and gradually 

 increasing in force and then decreasing." The object, or use of 

 the noise is very doubtful ; it is said that it attracts the 

 females to the males. " De gustibus non est disputandum ! " per- 

 haps, however, there may be some tender notes that we fail to 

 perceive ; and it may be that the absence of any definite organs 

 of hearing reduces the result of a steam-engine whistle to the 

 equivalent of an agreeable whisper. No special auditory organs 

 have been detected ^ as we have already intimated ; and certain 

 naturalists, amongst whom we may mention Giard, think that 

 the Insects do not hear in our sense of the word, but feel 

 rhythmical vibrations ; it is also recorded that though very shy 

 the Insects may be induced to approach any one who will stand 

 still and clap his hands — in good measure — within the range of 

 their sensibilities. There is a good deal of support to the idea 

 that the males sing in rivalry. 



Vocal structures. — Although we may not be able to pro- 

 nounce a final opinion as to the value to the Insect of the sounds, 

 yet we cannot withhold our admiration from the structures from 

 which they proceed. These are indeed so complex that they 

 must be ranked as amongst the most remarkable voice-organs in 

 the animal kingdom. They are totally different from the 

 stridulating organs that are found in many other Insects, and are 

 indeed quite peculiar to the Cicadidae. Some difference of 

 opinion has existed as to the manner in which the structures 

 act, but the account given by Carlet, some of whose figures we 

 reproduce, will, we believe, be found to be essentially correct. The 

 structures are partly thoracic and partly abdominal. On ex- 

 amining a male Cicada there will be seen on the under surface 

 two plates — the opercula — usually meeting in the middle line of 

 the body and overlapping the base of the abdomen to a greater 

 or less extent according to the species, sometimes nearly covering 

 this part of the body ; these are enlargements of the metathoracic 

 epimera ; they can be slightly moved away from the abdomen, 

 and, as tlie latter part is capable of a still greater extent of 

 movement, a wide fissure may be produced, displaying the complex 



1 Swintoii claims that one of the membranes in the vocal ajjparatus is an auditory 

 organ ; if so, the male -would he deafened by his own noise, while the females, not 

 possessing the organ, should not hear the song. 



