NOISES OF INSECTS. 497 
insects in the Cyclopedia of Anatomy and Physiology, has so admirably 
illustrated their structure, both internal and external, that this low jarring 
sound is owing to the shortness of the neryures, and the much greater 
number of those on the under side of the wing-covers being scored with 
the same notches as in a file (p. 928.) ; pointed out in the crickets by M. 
Goureau, who also saw them in the mole-cricket, but seems to have over- 
looked their extending to so many of the nervures as Mr. Newport has 
observed to be furnished with them, 
Another tribe of grasshoppers (Acrida, Pterophylla, &c.*) —the females 
of which are distinguished by their long ensiform ovipositor—like the 
crickets, make their noise by the friction of the bases of their elytra. And 
the chirping they thus produce is long, and seldom interrupted, which dis- 
tinguishes it from that of the common grasshoppers (Locusta). What is 
remarkable, the grasshopper lark (Sylvia locustella), which preys upon them, 
makes asimilar noise. Professor Lichtenstein, in the Linnean Tansac- 
tions, has called the attention of naturalists to the eye-like area in the 
right elytrum of the males of this genus*; but he seems not to have been 
aware that De Geer had noticed it before him as a sexual character ; who 
also, with good reason, supposes it to assist these animals in the sounds 
they produce. Speaking of Acrida viridissima—common with us—he 
says, “ In our male grasshoppers, in that part of the right elytrum which 
is folded horizontally over the trunk, there is a round plate made of very 
fine transparent membrane, resembling a little mirror or piece of tale, of 
the tension of a drum. This membrane is surrounded by a strong and 
prominent nervure, and is concealed under the fold of the left elytrum, 
which has also several prominent neryures answering to the margin of the 
membrane or ocellus, There is,” he further remarks, “ every reason to 
believe that the brisk movement with which the grasshopper rubs these 
nervures against each other produces a vibration in the membrane aug- 
menting the sound. The males in question sing continually in the hedges 
and trees during the months of July and August, especially towards 
sunset and part of the night. When any one approaches, they immediately 
cease their song.”* In these insects, as in the crickets, M. Goureau has 
detected in the strong horny ridge immediately behind the mirror or tym- 
panum, near the base of the upper surface of the left elytrum, the same 
transverse notches as in Acheta and Gryllotalpa, while on the under surface 
of the right elytrum a similar but less strongly notched file-like ridge is 
found ; and it is obviously by the rubbing of these rasps against the pro- 
jecting nervures of the borders of the wings, that the sounds resulting 
from the brisk friction of the elytra proceed. Dr. Burmeister conceives 
that they are chiefly caused by the forcible expiration of air from the 
thoracic tracheze and spiracles, first driven against the inflected external 
margin of the wing, and subsequently against the tympanum, which is thus 
caused to vibrate and resound ; but Mr. Newport has pointed out that 
this cannot be the cause, because in Acrida brachelytra the elytra are so ex- 
ceedingly short and narrow that they do not cover, nor are near, any part 
of the spiracles, so that the air in passing from these orifices cannot poss 
sibly be driven against the tympanum ; which, however, being accom- 
panied by notched nervures, as in A. viridissima, though differently arranged, 
1 See Kirby in Zool. Journ, p. iv. 429. 
® Linn. Trans. iv. 51, 5 De Geer, iii, 429, 
KK . 
