THE TIBIA OF ANTS. 233 



straight down the tibia, and fells again into the main 

 trachea just above the lower sac. 



The remarkable sacs (Fig. 9, 8 s) at the two ex- 

 tremities 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 con- 

 tracts (Fig. 9), there is, moreover, a conical striated 

 organ (a;), 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. In some cases I thought 

 I could perceive indications of bright rods, but I was 

 never able to make them out very clearly. This also 

 reminds us of a curious structure which is found in the 

 tibiae of Locustidae, between the trachea, the nerve, 

 and the outer wall, and which is well shown in some of 

 Dr. Graber's figures. 



On the whole, then, though the subject is still 

 involved in doubt, I am disposed to think that ants 

 perceive sounds which we cannot hear. 



The Sense of Smell. 



I have also made a number of experiments on the 

 power of smell possessed by ants. I dipped camel's-hair 

 brushes into peppermint-water, essence of cloves, laven- 

 der-water, and other strong scents, and suspended them 



