APRIL. 1906. THE CHEMICAL NATURE OF SOitE INSECT SECRETIONS. 27 



Our experiments were carried on with about a hundred large 

 specimens of Spiroboliis marginatiis 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 Spii'obolus 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 dift'uses into the lower alcohols, while less rapidlv 

 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 PtCl4, FeCl,, nor concen- 

 trated HNOo. When saponified with KOH the color changes to 

 the greenish red noticed in the decomposed aqueous extract, while 

 the odor disappears. The original odor can be brought back by 

 the addition of HCl, 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 



