48 THE DISPERSION OF THE GIPSY MOTH. 
to the large traffic by automobiles and trolley cars from the badly 
infested district in eastern Massachusetts, it is very probable that 
the infestation may have been brought about by the carriage of cater- 
pillars in this way. These colonies received careful attention during 
the summer. In the winter of 1908-9 16T estates were found in- 
fested with a total of 32 egg clusters. Fourteen of these estates 
were near Worcester Academy; the other two were in the eastern 
section of the city. Only a few egg clusters were found on the 
estates which were infested the previous year. In 1909-10 10 in- 
fested estates were found, with a total of 31 egg clusters, well scat- 
tered through the city. Only one of these was on property which 
was found infested the previous year. In 1910-11 275 egg clusters 
were found on 145 estates, every section of the city being included 
in the infested area. In 1911-12 3,570 egg clusters were found on 
424 estates. It seems probable that during the period from 1907 to 
1910 the greater part- of the infestation may have come from traffic, 
but one can not escape the conviction that during the summers of 
1910 and 1911, as the infestation to the south and southeast became 
more pronounced, a large number of the colonies resulted from wind 
spread. It should be remembered that the chances for spread by 
traffic in a large city are far greater than in the country districts. 
The data concerning Worcester are given because the city resembles 
many of the towns mentioned, inasmuch as it is very hilly, so that 
spread by air currents is very probable. 
The town of Millbury, which adjoins Worcester on the south, has 
a record which is of considerable interest, inasmuch as the infesta- 
tion has been decreasing from year to year. In the winter of 1907-8 
32 egg clusters were found on five estates. These were all located 
in the central part of the town not far from the railroad. The 
following year no new egg clusters were found in these localities, 
but two other infestations, containing 12 egg clusters, were located, 
one near an infestation of the previous year, close by the railroad, 
and the other a considerable distance west of any previous infesta- 
tion. In the winter of 1909-10 three new infestations were found, 
each containing an egg cluster, but no clusters were found in the old 
infested area. In the winter of 1910-11 nothing was found in the 
area infested the previous year, but three separate infestations, con- 
taining four egg clusters, were found in the Bond Hill section of 
the town east of the railroad. In 1911-12 33 egg clusters were found 
in six localities. The conditions in this town are quite different 
from those in any town previously mentioned. So far as is known, 
no bad infestations occurred in the region directly south, so that 
there would be far less opportunity for spread by the wind than 
would be the case in the other towns mentioned. It seems probable 
