15 
the caterpillars are carried by vehicles upon which they crawl or drop, 
or upon the clothes of passers-by, and in this way many trees upon 
which there were no egg masses become infested. 
The larval state lasts, on an average, from a month to five weeks. 
When full grown, the larve spin delicate grayish cocoons of silk mixed 
plentifully with hairs. The mixture of hair is brought about by the 
fact that the hairs are barbed and rather loosely attached to the body. 
When a caterpillar begins to spin its cocoon the hairs of its body and 
those of the long, black tufts on the prothorax first become entangled 
with the silken threads and are pulled out. By the time the cocoon has 


Fia. 6.—Tussock-moth caterpillar. Third and fourth stages, showing enlarged hairs from different 
parts of body (original). 
begun to take shape, the characteristic long, black tufts of hair have 
entirely disappeared from the body of the caterpillar. Later the 
shorter hairs of the sides of the body become entangled and removed, 
and finally many of the hairs composing the brush-like tufts upon 
the fore part of the body are pulled out, aud just before it transforms 
to pupa the caterpillar bears but a remote resemblance to the individ- 
ual before it began to spin. 
The barbed hairs just mentioned may occasionally produce consid- 
erable irritation of the skin of people upon whom the caterpillars may 
have crawled or dropped from the trees. The hairs from the different 
