532 NOISES OF INSECTS. 



the Cijclopcedia 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 nervures, 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 overlooked their 

 extending to so many of the nervures as Mr. Newport has observed to be 

 furnished with them. 



Another tribe of grasshoppers (^Acrida, Pterophylla, hc.^) — the females 

 of which are distinguished by their long ensiform ovipositor — like the 

 crickets, make their noise by the friction of the base of their elytra. And 

 the chirping they thus produce is long, and seldom interrupted, which 

 distinguishes it from that of the common grasshoppers (^Locnsta). What 

 is remarkable, the grasshopper lark (^Sylvia locustella), which preys upon 

 them, makes a similar noise. Professor Lichtenstein, in the Linncean 

 Transactions, 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 char- 

 acter ; who also, with good reason, supposes it to assist these animals in 

 the sounds they produce. Speaking of Acrida veridissima — 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 talc, 

 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 nervures 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 sur- 

 fiice 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 

 projecting 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 tho- 

 racic tracheae and spiracles, first driven against the inflected external mar- 

 gin 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 hrachelytra the elytra are so 

 exceedingly 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 

 possibly be driven against the tympanum ; which, however, being accom- 

 panied by notched nervures, as in A. viridissima, though differently 



' See Kirby in Zool. Juurn. p. iv. 429. * Linn. Trans, iv. 51. ^ De Geer, iii. 429. 



