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HEMIPTERA-HOMOPTERA 



structures. In order to see the parts it is better to cut away 

 an operculum ; underneath it three membranes can be seen, an 

 external, the timbal ; an anterior, the folded or soft membrane ; 

 and a posterior, the mirror. This last is a most beautiful object, 

 tensely stretched and pellucid, yet reflecting light so as to be 

 of varied colours ; there are also three stigmata, and some 

 chambers connected with the apparatus. The sound is primarily 

 produced by the vibrations of the timbal, to which a muscle is 

 attached ; the other membranes are probably also thrown into a 

 condition of vibration, and the whole skeleton of the Insect helps 

 to increase or modify the sound, which is probably also influenced 



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Fig. 281. — Musical apparatus of Cicada plebeia. (After Carlet.) A, Ventral view (Oper- 

 culum on right side is removed) ; ap, apophysis ; c, cavern ; c, trochantin (cheville 

 of Reaumur) ; ent, part of internal skeleton of abdomen ; mi, specular membrane ; 

 •in.pl, soft or folded membrane ; P, base of leg; st, st' , st", stigmata; t, drain 

 " timbale " ; v, operculum ; 1«, first, '2a, second abdominal segment : B, same seen 

 laterally, portion of abdominal wall as well as operculum removed ; A, point of 

 insertion of hind wing ; Mes, mesothorax ; sc, scutum of metathorax ; 3«, third 

 abdominal segment ; rest as in A. 



by the position of the opercula. The stigmata probably play an 

 important part by regulating the tension of the air in the 

 chambers. In the female some of the structures are present in 

 a rudimentary form, but there are no muscles, and this sex 

 appears to be really quite voiceless. 



Fam. 2. Fulgoridae. — Ocelli two {rarely three, or entirely 

 obsolete), placed beneath the eyes or near the eyes, usually in 

 cavities of the cheeks, antennae placed beneath the eyes, very variable 

 in form ; usually of two joints terminated by a very fine hair, 

 the second joint with a peculiar texture of the xihfuce, owing to the 

 existence of sensitive structures (Hansen). Form of head very 

 diverse; vertex and face forming either a continuous curve, or the 

 'planes of the vertex and face forming an acute angle, or both pro- 



