1907.] PUBLIC DOCUMENT No. 73. 153 



BKOWN-TAIL MOTH POISONING. 



The highly poisonous properties of the brown-tail moth cater- 

 pillars are only too well known to suffering humanity in east- 

 ern Massachusetts. This poisonous quality appears in the tiny 

 caterpillars in the webs, continues with increasing force as the 

 caterpillars approach maturity, and is also present in full viru- 

 lence in the cocoons and to some extent in the female moths. It 

 is caused by the development of certain poisonous hairs on the 

 body of the caterpillar, which are later cast off in molting or 

 in spinning the cocoon, and which also become attached in 

 greater or less numbers to the body of the moth in its struggles 

 while emerging from the cocoon. Naturally, from the large 

 tuft of hairs at the tip of the body of the female moth, the 

 winged insects of this sex are more poisonous than the males. 

 Indeed, in certain years, at the height of the flying season of the 

 brown-tail moth, motormen in charge of electric cars in country 

 districts, where high-power searchlights are commonly used, 

 have been obliged to wear gloves and veils to protect their faces 

 and hands from the winged insects which were attracted by 

 the rays of the strong lights on the front of the car. 



Our investigations, together with those of many physicians, 

 have shown that this poisoning soon spreads from a single point 

 of infection over a considerable part of the body, and for this 

 reason it has been generally believed that the hairs possessed 

 some poisonous principle which was absorbed by the blood and 

 was thus diffused over a greater or less area, causing the well- 

 known and highly painful irritation. On the other hand, in- 

 vestigations made some ten years ago by Mr. F. J. Smith, for- 

 merly instructor of chemistry at the Massachusetts Agricultural 

 College, gave only negative results, so far as determining the 

 presence of any poisonous principle. Mr. Smith tested the 

 caterpillar hairs with a wide range of solvents, and could find 

 no organic acids or alkaloids. To quote from his report, his 

 opinion was : " Hence, I am led to believe that the irritation is 

 of a mechanical nature, caused by the brittle, finely barbed 

 hairs, and not due to a toxic principle." Mr. Smith's studies 

 were in no sense complete, but these results were accepted for a 

 time as based on the only effort made by a competent chemist 



