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TEXT-BOOK OF ENTOMOLOGY 



trachea passes close to the tympanum, which thus has air on both 

 sides of it : the open air on the outer, the air of the trachea on its 

 inner surface. In fact, as Lubbock states, " the trachea acts like the 



Eustachian tube in our own ear ; it main- 

 tains an equilibrium of pressure on each 

 side of the tympanum, and enables it 

 freely to transmit the atmospheric vibra- 

 tions." 



These trachea, says Graber, though formed 

 on a similar plan, present many variations, cor- 

 responding to those of the tympana, and showing 

 that the tympana and the trachea stand in 

 intimate connection with one another. For 

 instance, in those species where the tympana are 

 equal, the trachea are so likewise ; in Gryllotalpa, 

 where the front tympanum only is developed, 

 though both tracheal branches are present, the 

 front one is much larger than the other; and 

 where there is no tym- 

 panum, the trachea remains 

 comparatively small, and 

 even in some cases undi- 

 vided(Lubbock,ex Graber). 



The acoustic nerve, 

 which next to the optic 

 is the thickest in the 

 body, divides soon after 

 entering the tibia into 

 two branches, one al- 

 most immediately 

 forming a ganglion, the 

 supratympanal gangli- 

 on, the other passing 

 down to the tympa- 



Uko 



rod 



Fm. 



Fio. 293. The auditory apparatus 

 In the tibia of a grasshopper, showing 



204. Auditory 



(r 1' IfU HX t' i 1'itl i Xxi- 



f<l, auditory rod ; 

 ko, terminal piece. 

 mini, Where it expands After Graber, from Lub- 



flat 



bock. 



organ; 5JV, nerve of the organ of Sie- 



bold; <?r, group of vesicles of same; 



,sv;. in-i-M- endings of the same; rT, 

 front tympanum ; / 7V, front branch 

 of tin- t'rachi-a: // '/', hinder tympanum : 

 hTf, hinder branch of tin- tra'-ln-a ; 



into an elongated 



the tympanal nerve-endings in situ: . 



ERL terminal veMcles of Sit-buM's gailgllOU, the Ol'gaU OI 0160010. (.P Ig. ^ 



C i IT **! ~f C! 



and closely applied to the anterior 

 tracheae. 



At the upper part of the ganglion is a 

 group terminating below in a single row 

 of vesicles, the first few of which are 

 approximately equal, but which subse- 

 by author.)- quent i y diminish regularly in size. Each 



