AUDITORY AND SOUND-PRODUCING MECHANISMS. 601 
Miiller’s organ both in form and structure; it is situated on 
the tracheal sac beneath the tympanic membrane. The crista 
consists of a ridge which extends from the bulb, in a longitudinal 
direction, over the sac. 
which become smaller as they recede from 
the bulb. These cells enclose the enlarged 
capitella of the chordotonal threads. The 
chordotonal ligaments extend from the 
cuboid cells to the adjacent integument. 
The ligaments are longest at the proximal 
end of the crista, that nearest to the bulb, 
and become gradually shortened as they 
approach the distal end of the crista. The 
chordotonal rods are frequently bent at right 
angles, where they join the capitella, and are 
sometimes jointed in the middle. 
The Supratympanie Organ (Graber’s organ) 
(Fig. 78) resembles a large Miillerian organ, 
which is fan-shaped in section. It is at- 
tached to the integument, near the tympanic 
membrane, and lies upona ganglion, in which 
a branch of the auditory nerve terminates. 
It is only indirectly connected with the tym- 
panic membrane and its air-sac through the 
medium of the circulating fluid; it lies ina 
distinct blood sinus, one of the walls of 
which is formed by the tracheal air-sac. 
The Mirrors of the Locustide are thin, tense 
areole of a circular form, situated on the 
base of the elytra of the sound-producing 
males, They are usually regarded as organs 
for the intensification of the sound produced 
—resonating organs. 
This ridge is formed of cuboid cells 
Fic, 
and tympanic (Sie- 
77-—The crista 
bold’s) organ of 
Lphippigera vitium, 
Serv., after Graber 
[283] : cv, the bulb 
of the crista acous- 
tica; at, pt, an- 
terior and posterior 
tympanic mem- 
branes ; 7, auditory 
nerve. 
This view of their nature is rendered 
more probable since these insects possess ear-like organs on 
the anterior tibize in both sexes. 
The Mirrors and Tymbals of the Cicade are situated in 
special cavities on the sides and below the base of the 
