326 



ZOOLOGY. 



sound, heard and appreciated by individuals of the other 

 sex. Any insect which produces a sound must be supposed to 

 have ears to hear the sound pro- 

 duced by others of its species. 

 In the antennae, palpi, and 

 abdominal appendages of dif- 

 ferent insects are seated mi- 

 nute olfactory organs consisting 

 of pits alone (Fig. 285), or of 

 hairs perforated at the end, and 

 pegs associated with the pits. 

 The ears (or auditory sacs) of the locust are situated, one 

 on each side, on the basal joint of the abdomen, just be- 



Fig. 286. Ear of a locust (Caloptemw ifolicus) seen from the inner side. T, tym- 

 panum ; TS, its border ; o, u, two horn-like processes ; bi. pear-shaped vesicle ; n, 

 auditory nerve ; ga, terminal ganglion; st, stigma ; m, opening and m' closing mus- 

 cle of the same ; M, tensor muscle of the tympanum-membrane. After Graber. 



hind the first abdominal spiracle (Fig. 274). The ap- 

 paratus consists of a tense membrane, the tympanum, sur- 

 rounded by a horny ring (Fig. 286). " On the internal sur- 



