108 PECULIAR STRUCTURE IN LEG OF ANT 



trachefe of the tibia are dilated, sometimes with a 

 recurrent branch. The same is the case even in some 

 mites. I will, however, reserve what I have to say on 

 this subject, with reference to other insects, for another 

 occasion, and will at present confine myself to the ants. 

 If we examine the tibia, say of Lasius jlavus, we shall 

 see that the trachea presents a remarkable arrange- 

 ment (rig. 69), which at once reminds us of that which 

 occurs in Gryllus and other Orthoptera. In the femur 

 it has a diameter of about ^j/o g ^^ ^'^ inch ; as soon, 

 however, as it enters the tibia, it swells to a diameter 

 of about 5^ of an inch, then contracts again to g^-Q, 

 and then again, at the apical extremity of the tibia, 

 once more expands to g^,,-. Moreover, as in Gryllus, 

 so also in Formica, a small branch rises from the upper 

 sac, runs almost straight down the tibia, and falls 

 again into the main trachea just above the lower sac. 



" The remarkable sacs (Fig. 69, S, S) at the two 

 extremities of the trachea in the tibia may also be well 

 seen in other transparent species, such, for instance, as 

 Myrmica ruginodis and Pheidole megacephala. 



" At the place where the upper tracheal sac contracts 

 (Fig. 69) there is, moreover, a conical striated organ (x), 

 which is situated at the back of the leg, just at the 

 apical end of the upper tracheal sac. The broad base 

 lies against the external wall of the leg, and the 

 fibres converge inwards. Indications of bright rods 

 may also be perceived, but I was never able to make 

 them out very clearly." 



This closely resembles both in structure and position 

 the supra-tympanal auditory organ of the Orthoptera. 



Graber has entirely confii'med this account and dis- 

 covered some insects in which the structure is more 



