8 THE DISPERSION OF THE GIPSY MOTH. 
While the gipsy moth does not belong to the same class as the 
scale insects just mentioned, it resembles them inasmuch as it is not 
spread by the flying of the adult, for although the females are pro- 
vided with wings, they are unable to fly, owing to the extreme weight 
of the body. Dispersion, therefore, is greatly restricted in this stage 
of the existence of the insect, and this is important, as it bears directly 
on the control of the species. 
INVESTIGATIONS OF THE DISPERSION OF THE GIPSY MOTH. 
Investigations which were carried on during the early nineties 
have been fully treated in the report on the gipsy moth by For- 
bush and Fernald, published by the Massachusetts State Board of 
Agriculture in 1896, natural and artificial dispersion being con- 
sidered on pages 9^116. Although it appeared at that time that 
excellent opportunities were afforded for studying the dispersion of 
this insect, still it must be remembered that the pest was abundant 
in relatively few localities during the years covered by that report, 
especially when the conditions existing in later years are considered 
in comparison. It is evident that the extent of distribution of any 
insect depends largely upon the abundance of the species, and if 
large areas are badly infested migration is often necessary in order 
that many of the individuals may secure sufficient food. 
The dispersion of the species, as treated in the above mentioned 
report, was considered as local and long distance. The former 
condition was brought about by egg clusters being broken and 
scattered by birds or other animals that frequent infested trees. 
Clusters were also carried on driftwood (see PI. I), and those 
deposited on leaves (see PL II) were sometimes distributed by 
the wind. The caterpillars were occasionally found clinging to the 
bodies of animals or to the clothing of persons who had visited 
infested places and were carried short distances in this way. 
Many colonies were established in remote districts by the carriage of 
the larvae on vehicles, and egg clusters were sometimes transported 
on cordwood or lumber products shipped from infested forests. (See 
PL III.) The distribution of caterpillars upon vehicles was con- 
sidered so important when the gipsy-moth work was begun in 1891 
that inspectors were stationed along the main highways to stop and 
examine all vehicles and to destroy any caterpillars found before 
allowing them to pass out of the infested area. This precaution was 
entirely warranted in view of the discovery that many farms had 
become infested by the transportation of caterpillars on vehicles. 
Places infested in this manner, however, were usually occupied by 
milkmen, peddlers, swill gatherers, or persons whose business caused 
them to drive regularly to and from the city during the summer, or 
to neighborhoods that were badly infested with the gipsy moth. 
