INSECT VAEIETY. 221 



to either tymbal interiorly along the sides of the ventral integu- 

 ment of the first segment, the first two abdominal rings coalesce, 

 so as to leave two cavities closed beneath by the metathoracic 

 lamellar projections, or operculae [a, Fig. 5b) ; and the sternum 

 of the first is angular, forming with the circular ventral ring of 

 the second two semi-lunar orifices (Plate III., Fig. 5a, m, m ; 

 Plate VI., Fig. 5). To avoid further prolixity, as these parts 

 have been so frequently the theme of general description, and 

 since the tymbals, muscles, tendons, and other parts may be 

 recognised by any inquirer even in desiccated Cicadse, it will be 

 merely necessary to add that in ka//nif odes- the connection between 

 the metathoracic spiracle {s, Fig. 4, Plate VI.) and motive muscles 

 is exceptional. This orifice enters the vesicle by a short tracheal 

 pipe, which after debouching is continued by its branches across 

 the vacuum ; these meet the adjacent muscle at its centre, 

 penetrate and surround it, and, ascending, encircle the tendon. 



The regularity of the series of curved chitineous ridges that 

 cross the tymbals of phanerotympanous Cicadse might suggest 

 that these Homojdera produce their music by friction, and that 

 they should be classed with stridulators. That this is not the 

 case may be either deduced from the fact that in cryptotympa- 

 nous species these are rudimentary, and only semi- indurated ; 

 or it may be practically tested in the j^hanero tympanums by 

 dissevering the wings, when the superior surface of the tymbals 

 will be bared, and their sonorous action manifested as free 

 collapse and rebound of the tense vibratile membrane from 

 l)elow upwards, produced and regulated in fulness and tone, by 

 the varying tensions of the tendons of their twin and sj^ecial 

 motive muscular fascicles. In what measure the resultant 

 sound is due to the tymbal's action on the air external, or on 

 that enclosed in the long central air-bladders, is doubtful (m, m) ; 

 but since it is similarly produced by muscular vibration of the 

 integument, and is accompanied by respiratory abdominal move- 

 ments, it appears in direct connection with the vocal music 

 exemplified in Hymeno})tera and B'lptera. This latter action of 

 the abdomen, ruling the respiration, and effected by special 

 elevator and depressor muscles, has specific variation, and 

 appears to determine the rhythm of the notes. 



Thus the males of Hamatodes when they commence a fitful 



