APRIL, 1906. 
THE CHEMICAL NATURE OF SOME INSECT SECRETIONS. 
27 
Our experiments were carried on with about a hundred large 
specimens of Spirobolus marginatus Say. Although largely nega- 
tive we deem our results of interest, as they seem to be somewhat 
at variance with the conclusions arrived at by Dr. Cook. 
The animals were forced to secrete by roughly shaking them in 
tepid water. By this means the Spirobolus were not injured and 
could be reserved for a future experiment. After some ten 
extractions they were unable to elaborate any further secretion, 
although they were carefully fed in the meantime. The water thus 
acquired a strong pungent odor and a dull yellowish color, as the 
secretion is very readily soluble in water. On heating for a 
moment to about 80 or 90 degrees the yellow completely changes 
to brown and the odor is greatly modified, losing its pungency. 
The addition of a small amount of alcohol effects a similar change, 
and even on exposure to the air for a few hours the water-solution 
undergoes the same color-changes. If the solution be shaken 
with ether, chloroform, benzene, or carbon disulphide while it is 
still in the yellow stage, the secretion readily passes into the added 
solvent, tinging it intense yellow, and leaving the water colorless. 
The extraction by ether may even be hastened by the addition of 
some salt. 
It readily diffuses into the lower alcohols, while less rapidly 
into the higher, e. g., amyl alcohol acquires the same tint as the 
water-layer above only after twenty-four hours, and never absorbs 
more of the secretion than the water does. After decomposition 
has takn place (?. e., when the liquid is in the brown stage), a 
separation of the secretion cannot be effected by any of the named 
solvents. 
When an ether extraction is carefully evaporated, the secre- 
tion can be obtained in its original concentration. It is then 
extremely volatile and pungent, irritating the eyes causing 
them to lachrymate, much like bromine ; it has an atrociously 
acrid taste ; stains paper; cloth, and the skin a deep yellow, which 
passes to a permanent brown ; it is neither acid nor alkaline to 
indicators; it gives no reaction with PtCl 4 , FeCL, nor concen- 
trated HNOg. When saponified with KOH the color changes tc 
the greenish red noticed in the decomposed aqueous extract, while 
the odor disappears. The original odor can be brought back by 
the addition of HC1, although faintly at times. When dried in a 
sulphuric acid desiccator on a watch glass the secretion is 
absorbed by the acid, thus suggesting in connection with its 
peculiar odor, a nitrile; but so far all tests for nitrogen and sul- 
phur have proved negative. If the secretion be placed in a nearly 
