140 THE BEOWST-TAIL MOTH. 
blighted or scorched by fire (Fig. 27). At first they feed 
upon the leaf which bears the egg mass, but soon wander 
to others, returning at night to the original leaf. The little 
caterpillars are but a twelfth of an inch long when they 
first emerge, but in about five days they molt for the first 
time, after which they are about one fifth of an inch long. 
A week or so later a second molt occurs, though often this 
is within the winter web during the fall. Early in Sep- 
tember the young caterpillars instinctively commence to 
weave the nest or web, their winter home. It is made of 
the leaves upon which they have been feeding, usually in- 
cluding the old egg mass at the tip of the twig. The form 
and shape of the web varies with the position and the 
materials available. Exit holes are left open so that the 
caterpillars may go in and out as long as the weather is 
propitious, but are usually closed during the winter. 
MEANS OF DISTRIBUTION. 
The principal spread takes place through the flight of 
the moths just after emergence. "These insects fly freely 
and have a habit of soaring upward above the tree tops 
and buildings. When the moths in their nocturnal flights 
have thus risen in the air, they are often drifted by the 
wind over long distances." (Fernald and Kirkland.) 
Thus the strong winds of mid-July, 1897, are known to have 
carried the moths far northward from the point of origin 
in Massachusetts and similar winds were undoubtedly re- 
sponsible for the unusual spread northward and eastward 
in 1904. 
It should be noted in this connection that as the moths 
are strongly attracted by lights they usually swarm around 
the electric lights in the center of a town and are always 
found first in towns and cities, which become centers from 
which the surrounding country becomes infested. This is 
a fortunate feature of their spread, for being thus naturally 
concentrated it is much easier to control the pest on the 
few town trees than if scattered over the country. 
Due to this attraction by lights, the moths have often 
been spread by electric and railway cars, and possibly 
steamers, but particularly electrics, the moths flying into 
the cars and being carried some distance. It has been no- 
ticeable in a newly infested territory that the infestation 
runs along the electric car lines in advance of the main 
