28 THE DISPERSIOX OF THE GIPSY MOTH. 
On Mar 6 a large tray of caterpillars was placed in a room in 
direct sunlight and the temperature rose to 100° F. This resulted in 
abnormal activity, and many of the larvse spun a considerable quan- 
tity of silk. 
In order to check these experiments, Mr. Collins made a series of 
field observations in woodland in Melrose, Sauo'us. and Beading. 
FIELD OBSERVATIONS. 
May 13. 1911. visited woods east of the laboratory at Melrose Highlands, 
which had been badly infested and partially to wholly defoliated in 1909 and 
1910. Infestation not as bad this year. At 9.30 a. m. the temperature in the 
sun was 92° F. : in the shade, 84° F. 
All eggs have apparently hatched, and the caterpillars are in the first stage. 
There is plenty of foliage. Very little spinning was observed. In the afternoon 
of the same day visited badly infested woods in Saugus. Temperature. 96° F. 
in sun ; 84° F. in shade. A strong wind was blowing, which varied from 
northwest to southwest. First-stage caterpillars were spinning some. If a 
branch was shaken, they would spin down and be blown away. ' 
On the following day observations were made at Reading. Mass. The tem- 
perature ranged froin 85° F. in the sun to 79° F. in the shade: the wind was 
west and southwest, but rather cool. First-stage caterpillars were feeding 
steadily and spinning freely. Twenty very small first-stage larvae and two that 
were nearly ready to molt were observed spinning down from a white-oak tree. 
Threads from 2 to 4 feet long were noted, but it was very difficult to determine 
the quantity of silk spun, as it is almost invisible. A considerable quantity 
of silk was noticed among the small twigs and branches on this tree, therefore 
it is evident that frequent spinning had been attempted by the larvae. 
Although few field observations were made to determine the tem- 
perature at which gipsy-moth caterpillars are active, it is evident that 
the results do not vary greatly from those carried on in the labora- 
tory. Experiments show that there is practically no activity when the 
temperature is below 60° F., and that only a part of the caterpillars 
move about at 65° F. Above this point activity increases rapidly. 
RELATION OF ACTIVITY TO THE SPINNING OF SILK. 
The above experiments show that the activity of the caterpillars 
is governed by the temperature, and it is obvious that the spinning 
of silk depends largely upon the activity of the larvae and hence 
upon the temperature. There are other factors, however, that enter 
into the problem, and these must be considered with the element of 
temperature. They are : 
Location where eggs are deposited. 
Degree of infestation. 
Kind of food plants. 
Condition of food plants. 
Direction and character of the wind. 
LOCATIONS WHERE EGG CLUSTERS ARE DEPOSITED. 
The egg clusters of the gipsy moth are not always deposited on 
the plant which furnishes the food for the previous generation. In 
fact, when the caterpillars are nearly ready to transform they usually . 
