86 NATURAL HISTORY OF WASPS. 
are guided by this faculty; and the only question is 
where the sense of smell resides. As the odorous 
particles are conveyed by the air to the organ of 
smell in air-breathing animals, the respiratory move- 
ments, which draw the air, have an obvious mecha- 
nical connection with the exercise of this faculty. 
But the connection of the sense of smell with the 
sense and organ of taste is certainly much closer 
than with the lungs. All the analogies of the higher 
animals, all that we know of ourselves, all that ex- 
periments seem to show, pomt to the mouth, rather 
than the general tracheal system, as being the seat 
of the sense of smell in insects. And experimental 
observation rather favours this conclusion. Bees 
were repelled by turpentine placed before their 
mouth, but not by the same being placed near their 
spiracles.* Smelling with the lungs, which must be 
very like smelling with the tracheaee—if insects really 
can do this at all—is a process with which many of 
us may have been painfully familiar, Hvery ana- 
tomist knows what it is to taste a smell, when the 
blood has been saturated with the poisonous air of 
the dissecting room, and how different this is from 
smelling in the ordinary way by the nose. But 
insect smell must be something much more acute 
than this, and of much more definite application. 
The difficulty is to understand how so small a surface 
as an insect’s mouth offers, with a limited afflux of 
odorous particles, can be so sensitive an instrument 
as by its capacities we know the organ of an insect’s 
smell to be.T 
* Van Der Hoeven, ‘ Handbook of Zoology,’ Vol. I, p. 281. 
+ ‘Burmeister Entomology. Trans.,’ p. 485, dismissing Kirby and ~ 
