76 STRIUULATING ORGANS AND THE EAR. 



become sufficiently dry and stiffened to enable the insect to 

 move about with ease ; and in another hour, with appetite 

 sharpened by long fast, it joins its voracious comrades and 

 tries its new jaws. The molting period, especially the last, 

 is a A'ery critical one, and during the helplessness that be- 

 longs to it the unfortunate locust falls a prej^ to many 

 enemies which otherwise would not molest it, and not in- 

 frequently to the voracity of the more active individuals of 

 its own species." 



The first three skins are most frequently shed on or near 

 the ground, under grass in little depressions, or under any 

 other shelter that ma}^ offer. The last molts take place 

 above the ground, as the insects like to fasten to some ele- 

 vated object. The bod\^ is very soft and colorless after each 

 molt, but soon hardens and shows the characteristic colors 

 and markings of the species. 



STRIDULATING ORGANS AND THE EAR. 



Man\- of the orthopterous insects are musicians. Only 

 earwigs, cockroaches, walking-sticks and praying-mantes 

 possess no organs to produce sounds. The females of 

 all orthopterous insects are voiceless. Such sounds do 

 not correspond to our voice, as they are simply produced by 

 friction. The organs by w^hich such stridulating sounds are 

 made are different in different families; they are very simple 

 in some, but complex in others. The true locusts {Acrid- 

 idse) produce sounds by rubbing the inner surface of the hind 

 legs against the outer surface of the wing-covers. "With 

 these insects there is a thickening of one of the main longi- 

 tudinal veins in the center of the wing-cover {vena radialis), 

 and a remarkable extension of the two areas between this 

 vein and the costal margin of the wing-cover {area scapu- 

 laris and area externomedia) , which serves as a sounding 

 board and which is wanting in the female. The most com- 

 mon representatives of the insects which stridulate in this 



