1879. | Zoology. 323 
arrangement for that purpose. This arrangement we find on the 
under side of the wing-cases. 
From a protuberance on the 
under-side of the coriaceous 
extremity, and situated on the 
inner or sutural edge, there is a 
large tracheal tube which ex- 
tends out laterally, thence for- 
ward and terminates at the junc- 
ture of the wing-case with the 
thorax. Thistracheal tube forms, Fig. 2—4’, more enlarged view of the vi- 
or extends through a ridge on bratory flanges ; d”, scaly leather-like mem- 
the inferior surface of the case, brane. 
which is in the form of a quadrant or crescent. On the ridge is 
situated a series of minute transverse vibratory flanges, resting 
upon edge and resembling, to a certain extent, the scales of a fish 
when scraped so as to cause them to stand erect. The base of 
each flange is thickened, the upper edge slightly blunted and re- 
curved. The upper surface of the wing-case is squamous, so that 
when either case is drawn over the other, the series of vibratory 
flanges on the under side of one is made to pass rapidly over the 
scaly upper surface of the underlying case, in this manner pro- 
ducing the harsh creaking sound so familiar. By a greater or 
less rapidity of motion the insect can produce the variations of 
tone which are often observed. As the cases do not unite in the 
center of the back but each passes nearly to the opposite side of 
the body, the chain of vibratory flanges can be utilized to nearly 
its full length, before it becomes necessary to re-commence the 
the anterior portion of the cases. The leathery covering of this 
Space is slightly elevated, forming a chamber underneath, which 
prevents the sound from being smothered in the folds of the second 
pair of wings, which lie directly beneath. The insect when 
about to produce its call usually assumes a fixed, statue-like posi- 
tion, with head lowered and posterior extremities slightly elevated, 
the cases forming an angle of twenty or thirty degrees with the 
abdomen. 
The call is formed during the outward stroke of the cases, they 
being slightly separated when returning to the first position. I 
abode, stood with the head in the burrow and the extremities of 
.the wings protruding from the opening, thus seeming to compre- 
hend that their call could be heard to a greater distance if stand- 
ing in this position than if in the reve as 
