212 
Psyche 
[December 
in a curious manner. First one antenna was pushed down with 
the fore legs, caught near the base and rapidly passed through 
the mouth parts clear to the tip when it was released and the 
procedure repeated with the other antenna. This apparent 
cleaning of the antennae continued indefinitely, or until the 
animals became completely anaesthetized. The maxillary and 
labial palps were also frequently drawn through the mouth. The 
same reactions occured when carbon tetrachloride vapor or bro- 
mine was used. Two inert esters, ethyl acetate and amyl acetate 
(banana oil) produced identical reactions. The animals simply 
responded to these volatilized substances with their antennae 
and palpi. No other reactions occurred until the anaesthetic 
effect through the spiracles became noticeable. These experi- 
ments, it seems to us, signify that chemoreceptors are located 
on the antennae and on the maxillary and labial palps. This, 
however, does not necessarily mean that these chemoreceptors 
are those of smell. The reactions obtained might very easliy 
represent merely the effect of violent chemical irritations such as 
the reaction of the human eye to onion oil or the reactions of the 
mucous membrane of the human mucosa to pollen particles. It 
seems unlikely, however, that two such inert substances as amyl 
and ethyl acetate could produce much irritation aside from ex- 
citing perhaps an obnoxious odor sensation in the insects. Never- 
theless, insect sense organs are constructed differently from those 
of higher animals. Their surfaces, as pointed out by Kennedy, 
are often external and on long processes. They are also dry and 
consequently the direct contact with a chemical stimulus, not 
first dissolved in mucous secretions, may explain the differences 
in behavior and the reason for the great sensitivity to such sti- 
muli. To meet the objection of simple chemical irritation and to 
prove that olfactory sensations are received through the antennae 
some additional experiments were performed. 
Two roaches with perfect antennae were segregated in an 
oblong cage having a glass top and a corked hole on each of 
two efids. These holes were ordinarily used for the introduction 
of food and water. Another pair of roaches with their antennae 
amputated at the base was placed in a similar cage. Each cage 
was completely divided in half by a double layer of a fine mesh 
