EAE OF LOCUSTS. 107 



ous or horny thickenings, a small triangular knob, and 

 a larger, somewhat complicated piece, consisting of two 

 processes — a shorter upper, and a longer lower one, 

 making a broad angle with one another. 



As in the preceding families, so also in the 

 Locustidse, the acoustic nerve is in close connection 

 with the trachesD ; it swells into a ganglion, which con- 

 tains in some species as many as 150 auditory rods, and 

 then, as in the supra-tympanal organ (see p. 105), con- 

 tracts into a tapering end, which is attached to the small 

 chitinous knob. The auditory rods differ in no respect, 

 as yet ascertained, from those already described. 



For many years no structure corresponding to the 

 tibial auditory organ of the Orthoptera was known in 

 any other insect. 



In 1877, however, I discovered * in ants a structure 

 which in some remarkable points resembles that of the 

 Orthoptera, and which I described as follows : — " The 

 large trachea of the leg (Fig. 69) is considerably 



Fig. 69.— Tibia of yellow ant (Lasius jflavus), x 15. S, S, Swellings of large trachea; 

 rt, email branch of trachea ; a, chordotonal organ. 



swollen in the tibia, and sends off, shortly after entering 

 the tibia, a branch which, after running for some time 

 parallel to the principal trunk, joins it again. 



"Now, I observed that in many other insects the 



* Lubbock, "On the Anatomy of Ants," Microscopical Journal, 



1877. 



