The Structure and Special Physiology of Insects 27 
come into actual contact with the special taste nerves, it is obvious 
that insects, to taste solid foods, have first to dissolve particles of these 
foods in the mouth-fluids, and that the taste-organs have to be situated 
in the mouth or so that they can be brought into it to explore the food, as 
are the movable, feeler-like palpi. What experimentation on the sense of 
taste in insects has been carried on shows that certain insects certainly taste 
food substances, and indicates that the sense is a common attribute of all 
insects. Lubbock’s many experiments with ants, bees, and wasps present 
convincing proof of the exercise of the taste sense by these insects. Forel 
mixed morphine and strychnine with honey, which ants, attracted by the 
honey smell, tasted and refused. Will’s experiments show that wasps 
recognize alum and quinine by taste. He found bees and wasps to have 
a more delicate gustatory sense than flies. 
Smell is probably the dominant special sense among insects. It exists 
at least in a degree of refinement among certain forms that is hardly 
equalled elsewhere in the animal kingdom. The smelling organs are micro¬ 
scopic pits and minute papillae seated usually and especially abundantly 
on the antennae, but probably also occurring to 
some extent on certain of the mouth-parts. The 
fact that the antennae are the principal, and in 
many insects the exclusive, seat of the olfactory 
organs has been proved by many experiments in 
removing the antennae or coating them with par¬ 
affine. Insects thus treated do not find food or 
each other. As substances to be smelled must 
actually come into contact, in finely divided con¬ 
dition, with the olfactory nerve-element, these 
pits and papillae are arranged so as to expose 
the nerve-end and yet protect it from the 
ruder contact with obstacles against which the 
antennae may strike. It is certain that most 
insects find their food by the sense of smell, and 
the antenna of a carrion-beetle (Fig. 54) shows 
plainly the special adaptation to make this sense 
highly effective. On the “leaves” of each antenna 
of June-beetleS nearly 40,000 olfactory pits occur. 
Some of the results of experimentation on smell 
indicate a delicacy and specialization of this sense 
hardly conceivable. A few examples will illustrate 
this. It is believed that ants find their way back 
to their nests by the sense of smell, and that 
they can recognize by scent among hundreds of individuals taken from 
Fig. 54. — Antenna of a 
carrion-beetle with the 
terminal three segments 
enlarged and flattened, 
and bearing many smell- 
ing-pits. (Photomicro¬ 
graph by George O. Mit¬ 
chell; much enlarged.) 
