10 FARMERS’ BULLETIN 564, 
The bodies of the caterpillars of the brown-tail moth are provided 
with poisonous hairs. A microscopic examination of these hairs 
shows that the edges are barbed in such a way that when they come 
as 
i ‘ fan 
\y 
Fic. 6.—Red oak trees stripped by brown-tail moth caterpillers. Note old winter 
webs at tops of trees. (Original.) 
in contact with the human skin and are pressed into the flesh, intense 
irritation is caused. These hairs are also hollow and contain a poi- 
sonous substance which acts on the blood corpuscles. This causes 
