SILK PRODUCED BY FIRST-STAGE GIPSY-MOTH LARVJE. 23 
during sudden squalls or sharp whirlwinds, provided the tempera- 
ture is high enough to cause the caterpillars to become active. Early 
in the spring it is quite common to see papers or leaves caught up 
by such winds and carried several hundred feet in the air. This 
often results in these objects coming in contact with strong currents 
high above the earth and being carried many miles before falling. 
Undoubtedly the same thing happens when caterpillars are sus- 
pended from the trees by the silk which they spin, although abso- 
lute proof of this point is very difficult to secure. Several other ele- 
ments have an important bearing on this matter, such as the density 
of infestation and the quantity of silk which is produced by the first - 
stage larva\ 
QUANTITY OP SILK PRODUCED BY FIRST-STAGE GIPSY-MOTH 
LARV.E. 
A record is given on page 331 of the report on the gipsy moth, 
by Messrs. Forbush and Fernald, of the quantity of silk produced by 
first-stage gipsy-moth larvae. The data were secured b}^ inducing the 
larvae to commence spinning, after which the end of the thread was 
attached to a reel, and the quantity produced was determined by 
multiplying the circumference by the number of revolutions which 
it was turned. In these experiments newly hatched caterpillars pro- 
duced the following quantities of silk : 4 feet 6 inches, 9 feet 7 inches, 
38 feet 2 inches, and 69 feet 4 inches. Older first-stage caterpillars 
spun : 53 feet 2 inches, 24 feet 2 inches, 3 feet 2 inches, 6 feet 4 inches, 
7 feet, 25 feet 3 inches, and 22 feet 6 inches. The record indicates 
that some of the caterpillars could not be induced to spin, but from 
the figures given the quantity of silk spun by newly hatched first- 
stage caterpillars ranged from 4 feet 6 inches to 69 feet 4 inches, 
giving an average of 30 feet 3 inches, while for caterpillars in the 
same stage that were a little older the record was from 3 feet 2 inches 
to 53 feet 2 inches, giving an average of 23 feet 8 inches. 
These experiments Avere repeated in the spring of 1911. An at- 
tempt was made to use a reel similar to the one already mentioned, 
but much difficulty was experienced, even when the larvae were 
placed in warm sunshine and when spinning was encouraged by 
using an electric fan to make a strong air current. It was found 
that no spinning would take place when the temperature Was low. 
Unless the larvae were constantly disturbed, they would climb up the 
threads which they had spun, and after this commenced it was diffi- 
cult to induce them to spin more or to prevent them from crawling 
up to the attachment on the reel. The same thing occurs in nature, 
and it is quite common to find first-stage caterpillars suspended 
from the trees bearing a small mass of white material beneath the 
mouth cavity or partly around the first pair of legs. Close examina- 
