APRIL, 1906. THE CHEMICAL NATURE OF SOME INSECT SECRETIONS. 
33 
color seems to be produced not by indol, however, but rather by 
the burnt chitin or animal fat, as other insects which did not have 
an indoloid odor gave the same result. The very delicate and 
characteristic test with strong hydrochloric acid and a pine 
splinter was also tried, but with negative results, as no red or 
purple color was developed. As it is not an indol and yet has a 
fecal odor it would seem that it must contain a leucin. Its solu- 
bility also indicates the presence of this substance since it is 
readily extracted from the ants by water or ether, but not at all 
by absolute alcohol. When an ethereal extraction of the ants is 
rapidly evaporated under reduced pressure a few pearly fat 
globules are obtained, which are in part soluble in water, while the 
addition of alcohol causes a globule to separate for a few moments 
(leucin and fat?), later to disappear. After evaporation of the 
alcohol from this and freezing the residue, some crystals very 
much resembling leucin could be observed under the microscope, 
although contaminated greatly and rendered somewhat obscure 
by the large amount of fat present in the mixture. These crystals 
were very distinct when the flask was cold, but as it became 
warmed up to the room temperature they melted or dissolved 
in the fat. 
The original ether extraction is neither acid nor alkaline to 
indicators, and on saponification with potassium hydroxide gives 
no odor of amonia, but a smell resembling cenanthol, which most 
probably arises from the fat and not from the odorous principle. 
Thus although there is no positive evidence that the substance 
present in Eciton is actually leucin, nothing seems to oppose such 
a conclusion. 
That the Eciton odor has considerable biological significance 
is very probable. These ants are totally blind, and migratory in 
their habits, so that they must depend almost entirely upon a 
sense of smell to follow one another about. Thus it can easily 
be seen how much a strong odor might be developed through the 
action of natural selection, from the small trace of leucin that is 
usually present in insect feces. (Concerning the normal pres- 
ence of leucin in the alimentary tract of insects see Plateau ('73).) 
II. FORELIUS FCETIDUS. 
The Texan species of this monotvpical genus, like the species 
of Tapinoma and a few other closely related ants, has a very 
strong and peculiar odor which has been very aptly described by 
Buckley ('66), and later by Forel, as closely resembling "rotten 
cocoanuts.'' 
