THE SONG OF THE CICADA. 
361 
1. The motor muscle of the drum (m m, fig. 1). — This is 
the most important. Reaumur, who discovered it, gave it no 
particular name, hut M. Solier termed it “ the musical muscle.” 
This name should he abandoned, as it shares the music-pro- 
ducing function with two other sets of muscles. According 
to Duges (op. cit. Tom. ii. p. 228), another muscle of the 
drum — u tres-petit, cache sous le bord inferieur du cadre de la 
timbale qui l’a derobe aux anatomistes, a pour usage peut-etre 
d’augmenter la tension de la timbale.” M. Carlet, however, 
does not believe in its existence, and promises to demonstrate 
that, even were it present, it would completely spoil the action 
of the musical apparatus. The tensor of the drum is the most 
bulky muscle in the Cicada’s body. It takes its fixed origin from 
the whole extent of the entogastric crest ; whence its fibres pass 
outwards and backwards to abut upon a disk, from which there 
proceeds a short tendon to a movable point of insertion upon the 
drum. At the junction of the two trunks of this muscular cone is 
to be seen a membrane which assumes the form of a half-ring {x, 
fig. 1 ). This goes horizontally to be inserted upon the tergum* at 
the junction of the first two abdominal somites, only leaving 
between itself and this part just space enough for the passage of 
the dorsal vessel. In conjunction with its fellow this membrane 
forms an oval rihg, allowing of communication between the cavi- 
ties of the thorax and abdomen. The fibres of the tensor of the 
drum are of the striped kind, and are inserted into an elliptical 
disk (“ plaque cartilagineuse ” of Reaumur), from which the 
triangular tendon arises, to be attached by a membranous tongue 
to the postero-inferior part of the rim of the drum. 
2. Tensor of the folded membrane. — This muscle, which M. 
Carlet believes that he was the first to describe, is cylindrical 
in form (m t, fig. 1 ), and has its fixed origin from the upper 
border of the frame of the drum, while its insertion ( movable ) 
is at the posterior part of the apophysis of the folded membrane. 
It, too, belongs to the striped variety ; and, as in the preceding 
muscle, between its fibres and the point of insertion there inter- 
venes a conical disk carrying a very short tendon. 
3. The sterno-entogastric muscle {ms, fig. 1).— This name 
is derived from the two points of origin and insertion. The 
muscle passes longitudinally from the apex of the entogastrium 
to a triangular projection springing from behind the upper point 
of the sternum of the metathorax. The fellow muscles lie very 
close to one another on the middle line, and communicate with 
the deep surface of the folded membrane. 
D. Sonorous Cavities . — Under this general term are comprised 
* The tergum is the upper or dorsal element, or factor, of a thoracic seg- 
ment, the insect being placed upon its legs. 
NEW SEEIES, VOL. I. NO. IV. B B 
