100 EAR OF GRASSHOPPERS. 



crickets Gryllidae, the grasshoppers Locustidae, and the 

 locusts Acridiidse.* 



In grasshoppers (Gryllida)) and crickets (Achetidse) 

 the auditory organ lies in the tibia of the anterior leg, 

 on both sides of which there is a disc (Fig, 63), generally 

 more or less oval in form, and differing from the rest 

 of the surface in consisting of a thin, tense, shining 

 membrane, surrounded wholly or partially by a sort of 

 frame or ridge. In some species the two tympana are 

 similar in form ; in others they differ. For instance, in 

 the field cricket, the hinder tympanum is elliptic, 

 the front one nearly circular in outline. 



In many of the Gryllidse, the tympana are protected 

 by a fold of the skin, which projects more or less over 

 them. The corresponding spiracle is also specially 

 modified in the stridulating locusts, while in those 

 which are dumb it is formed in the same manner as 

 the others. 



The tympana are not always present, and it is an 

 additional reason for regarding them as auditory organs, 

 that both among the Achetidse and the Gryllidse, in 

 those species which possess no stridulating organs, the 

 tympana are also wanting.f 



* The destructive " locust " of the East, which is so numerous tliat 

 in one year our Government^ in Cyprus destroyed no less than 

 150,000,000,000 of eggs, and whose ravages are used in Eastern poetry 

 as types of destructiveness, has short antennae, and belongs to the first 

 division ; to which, therefore, English entomologists apply the name 

 Locusta, while our foreign friends, on the contrary, apply the name to 

 a totally diflferent insect. However, I merely refer to this now, to explain 

 why the terms I have used do not in all cases agree with those 

 adopted by the observers to whom I am referring. 



t This rule seems, however, not to be entirely without exceptions. 

 At least, Aspidonotus and Hetrodes are said to possess tympana, but 



* Report on the Locust Campaign, Pari. Paper, 5250 of 1888. 



