134 
THE BROWN-TAIL MoTII. 
Observations made during January and February, 1907. 
showed that where the temperature falls to below 25° below 
zero Fahrenheit, that large numbers of the caterpillars in 
the average size nests are killed and that where it drops to 
-35° Fahr. nearly all may be killed in average size nests, 
but that those in 
the large nests 
on the oaks of 
700 to 900 cat- 
erpillars are not 
materially i in- 
jured by these 
1 o w tempera- 
tures. 
E x p e riments 
have proven 
that there is 
almost no possi- 
bility of the cat- 
erpillars being 
caused to emerge 
in midwinter by 
several unusual- 
ly warm days 
such as occurred 
January 21-23, 
1906, at which 
time the news- 
papers surmised 
that the cater- 
pillars would emerge and be killed by subsequent cold. 
When they first emerge from the winter nest the young 
caterpillars are of a blackish color, covered with warm 
brown or reddish-brown hairs. The head is jet black, 
while the body is marked with yellow when seen under a 
lens. Projecting from the back of the fourth and fifth 
segments is a large tuft of reddish-brown hairs, looking 
Fig. 20.— Small Brown-Tail Moth caterpillars emerging 
from the winter web and feeding on the leaves of 
its surface. 
