235 
Antenna: of Insects. 
and its immediate contact by that of touching with the palpi and 
antennae ; but I remarked nothing that could in the least induce 
me to suppose that the olfactory sense resides in the antennae, or 
even in the spiracles of the body, as some have supposed.* If 
this were the case we might reasonably have expected that the 
insect would soonest have discovered its food when it lay on one 
side of it in a line with the spiracles or with one of the antennae, 
and not when directly in front. On the contrary, the insect fre- 
quently moved in an opposite direction, and seemed to find its 
food most readily when placed, although at a greater distance, 
directly in front of it. Hence a question naturally arises, if it be 
neither in the spiracles nor the antennae, where does the sense of 
smelling reside? Analogy teaches us to search for it in the head, 
as suggested by that excellent and venerable naturalist the Rev. 
W. Kirby, the father of English entomologists, and where after 
all, perhaps, it may be found. 
Animals inhabiting water have the faculty of smelling equally 
with those which inhabit the atmosphere. This is proved from 
the known fact that odoriferous substances, often used by poachers 
as bait, when thrown into ponds or rivers attract fishes from a 
great distance, in the same manner as they would attract birds 
or quadrupeds in the atmospheric air. And here I may notice a 
striking instance of the existence of this faculty in water-beetles, 
previously to detailing experiments on them with regard to the 
use of their antennae. 
Towards the latter part of the summer of 1830 I frequently 
observed many different species of water insects, particularly 
Dytici, Notonectce, and water Cimices, sticking to the sides, and 
lying beneath the wall of an outhouse that had been recently co- 
vered with coal tar, and I was awhile in doubt to know what 
could have attracted so many of such different species to that 
particular spot, which was at a considerable distance from their 
natural haunts, there being neither dike nor pond within nearly a 
quarter of a mile. It at length occurred to me that they must 
certainly have been attracted thither by the tar, which, it is well 
known, emits an odour of carburetted hydrogen gas, and which 
gas is also abundantly formed in stagnant pools and dikes, the 
usual habitations of those insects. What tends in a measure to 
confirm my opinion is, that although at the present time (April, 
1831), after an interval of nine months from the date alluded to, 
the odour of the tar is considerably diminished, the same species 
are still attracted to the spot, and have not been observed on any 
* Cuvier and Lelimann. 
