38 THE BROWN-TAIL MOTH. 



cocoons have been abundant has retained for months the power of 

 thus affecting any tender-skinned person rashly assaulting it with 

 the beating-stick. Mr. H. Moncreaff noticed a larva rubbing its 

 hairs across the scarlet tubercles on its back, and upon examina- 

 tion found at the base of each tubercle a valve, opening to a 

 gland from which an oily substance exuded. This oily substance 

 he found, on being applied to the skin, to produce at once inflam- 

 matory swellings, and all the irritation usually caused by contact 

 with the hairs. 



It is well known both to entomologists and to the layman 

 that certain insects carry specific poisons, Avhich when in- 

 jected beneath the skin cause acute pain. Bees, wasps, 

 mosquitoes, bedbugs and other insects fall in this class ; and 

 chemical investigations have shown that the poisonous prin- 

 ciples are usually well-defined organic compounds, capable 

 of being recognized by chemical tests. This being the case, 

 it was at first supposed that the hairs of the caterpillars con- 

 tained such a principle, and that the chemist of the gypsy 

 moth conmiittee, Mr. F. J. Smith, M.S., would soon deter- 

 mine its nature. A large amount of material, such as 

 liairs, cocoons and molted skins, was submitted to Mr. 

 Smith, who extracted them with various solvents with the 

 lollowiiig results, whicli we quote from Mr. Smith's notes : — 



I made a number of extracts of the hairs with each of the re- 

 • agents mentioned below, some of the extracts being of the hairs 

 alone, others of the molted skins, and still others of the cocoons 

 which contained hairs in great numbers. The reagents used were : 

 water, alcohol, ether, chloroform, petroleum ether, acetone, acetic 

 ether, dilute sulphuric acid, dilute caustic potash. I tested each 

 of the extracts after digesting for some hours, and in each case 

 they nettled the skin. On the other hand, the filtered extracts 

 (freed from the hairs) caused no irritation of any sort when ap- 

 plied even where the skin was broken. Careful chemical tests 

 failed to show the presence of any organic acids or alkaloids. 

 liunce I am led to believe that the irritation is of a mechanical 

 nature, caused by tiie brittle, liuely barbed hairs, and not due to 

 a toxic principle. 



Before submitting the material to Mr. Smith, we had 

 already discovered tiiat tlie irritation was not caused by 



