3i6 



LOCUSTIDAE 



CHAP. 



muscular attachments ; B is a transverse section of the organ. In 

 these figures the different parts of the appendages bear the same 

 lettering as they do in Fig. 191. It will be seen that in the com- 

 pleted structures the parts d have become very intimately con- 

 nected with the parts V and V , which belong to another segment. 

 The Locustidae resemble the Acridiidae in the possession of 

 specialised ears and sound-producing organs ; neither of these is, 

 however, situate in the same part of the body as in Acridiidae. 



The ears of Locustidae are 

 placed on the front legs, below 

 the knee ; a tympanum (Fig. 

 193, A), or a crack gi^dng en- 

 trance to a cavity in which the 

 tympanum is placed (Fig. 193, 

 B), being seen on each side of 

 each of the anterior pair of 

 limbs. In this family, as in 

 the Acridiidae, three kinds of 

 ear are recognised according to 

 the condition of the tympanum, 

 ^ ^ which is either exposed (Fig. 



Fig. 193. Ears of Locustidae : A, portion -,r>o an i i i 



of front leg of Odontura semcauda, 19'^. ^) Or ClOSecl by an OVCr- 



adult ; p, prominence of integument ; r, growth of the integument (Fig. 



rim of ear ; T, tympanum ; J, thickened 5'^o-r)\ t- ^ 



area thereof; Fti, remains of groove in 193, b), Or m a Condition to a 



which the structure was developed. B, certain extent different from 



portion of front leg of Thamnotnzon 



apterus ; *, inner margin ; a, slit - like either of thcSC. The existence ol 



external aperture of ear ; di, overlapping ^.^^^ ^^^^^ ^^^ ^^^^ ^ ig ^ ^^^^_ 

 cover of the ear. (Alter Graber.) ^ . . ^ 



ous fact, but it is beyond doubt 

 in the Locustidae, and there is good reason for believing that analo- 

 gous organs exist in this situation in other Insects that have special 

 means of sound-production, such as the ants and the Termites. 



The structure of these organs in the Locustidae has been 

 investigated by Graber,^ and their acoustic functions placed 

 beyond doubt, though to what special kind of sounds they may 

 be sensitive is not ascertained, this point being surrounded by 

 even greater difficulties than those we have discussed in the case 

 of the Acridiidae. In the Locustidae there is a special structure 

 of a remarkable nature in connexion with the ears. In Acridiidae 



^ Ardi.f. mikr. Anat. xx. 1882, and xxi. See also von Adelung, ZcUschr. wiss. 

 Zool. liv. 1892, p. 316. 



