126 THE BROWN-TAIL MOTH 



with an intense irritation, then an eruption appeared, re- 

 sembling eczema, with a sort of watery blister on the top. 

 There was intense irritation all over the body, on the head, 

 arms and limbs. I saw numbers and numbers of eases of 

 this poisoning; I should say nearly a hundred eases in all 

 came under my observation. The irritation seemed to re- 

 main and was much worse than that caused by poison oak or 

 poison ivy, and was not so easily gotten rid of. I treated 

 most eases with some cooling application. Some eases were 

 decidedly obstinate, but no case was serious enough to men- 

 ace the life of the patient." 



Investigations by Massachusetts authorities of this con- 

 sequence of the presence of the brown-tail moth showed that 

 it was due to the mechanical irritation of the barbs of cer- 

 tain short hairs on the body of the caterpillar; these hairs 

 are called the nettling-hairs. "These nettling-hairs are 

 very small, only about one two hundred and fiftieth of an 

 inch in length, very sharp at one end, and with two or three 

 barbs at the other end and many along the sides. These 

 barbs are so arranged that when these nettling-hairs fall 

 upon the skin any movement will cause them to work into 

 the flesh. The nettling of the skin may be caused by con- 

 tact with the caterpillars in either of the last two molts, 

 the cocoons, and to some extent with the moths, but contact 

 is not necessary, as these fine nettling spines may fall or 

 be blown by the wind." 



The true nettling hairs are the short brown hairs giving 

 the tubercles of the back and sides of the abdomen a brown 

 velvety appearance, shown in figure 12 at 3, and do not 

 appear until the last two stages of the caterpillar's growth. 

 Nettling may be produced, however, as we have learned 

 from experience, by the younger stages, even those in the 

 webs, where they are freely handled by one with a tender 

 skin. No inconvenience would occur to anyone, however, 

 from handling the unopened webs, and rarely will the young 

 caterpillars be annoying. 



