104 THE GYPSY MOTH. 



abundant in Medford. These years of its greatest abundance 

 were also the years of its greatest diffusion, for during the 

 period when it was most numerous on trees, about buildings 

 and along highways, many more caterpillars were carried out 

 on vehicles from the worst infested localities than at any time 

 before or since. From the small size and general appear- 

 ance of most of the colonies found in 1891 at a distance from 

 Medford, it was apparent that they had originated but two 

 or three seasons previous to that time. On further inspec- 

 tion it became evident that the moth had become widely 

 distributed in 1888, 1889 and 1890 over the region occu- 

 pied by it in 1891. 



Most of this diffusion to a distance from Maiden and 

 Medford was accounted for by teaming and driving to and 

 from the district originally infested. Therefore, it may be 

 termed the primary distribution, as it was caused by trans- 

 portation direct from the towns first infested. Here and 

 there, however, large colonies were found that must have 

 been growing for eight or ten years. These colonies, if on 

 or near highways, had already become centres of infestation 

 from which the moths had been distributed widely, not only 

 along the roads leading out of the infested locality but also 

 back toward the originally infested centre by means of 

 vehicles bound toward Boston. This spreading from these 

 colonies may be called a secondary diffusion. Of this there 

 are some interesting examples. From the large colony 

 in Swampscott (see page 58) the moths were not only dis- 

 tributed on to Marblehead but they were also taken back 

 into Lynn. The Lynn residence of the owner of the place 

 where the Swampscott colony was situated was found in 1892 

 to have been recently infested, and it was learned that the 

 owner had been accustomed to drive frequently to the 

 Swampscott place and leave his horse and buggy in the yard 

 under the infested trees. 



Early in 1891 a colony was found in North Cambridge in 

 the yard of MuUer Brothers' tannery. As thirty-five thousand 

 egg-clusters were taken there the colony must have originated 

 several years previous to 1891. Dead horses were frequently 

 carted from Maiden and Medford to the Muller place, where 

 there were at that time facilities for making such use of these 



