THE DISPERSION OF THE GIPSY MOTH, 
INTRODUCTION. 
The dispersion of any insect that has been introduced, accidentally 
or otherwise, into a new country offers an interesting opportunity to 
study the elements which aid in bringing about its transmission from 
point to point within that country, and this is particularly true con- 
cerning one of so great economic importance as is the gipsy moth. 
When the first work to suppress this insect was taken up in the early 
nineties an attempt was made to determine all the means by which 
the insect was spread, and since that time any data bearing on the 
spread of the pest have been eagerly sought and carefully studied in 
the hope that better methods could be found for its control. The 
region surrounding Medford, Mass., where the gipsy moth was in- 
troduced in 1869, is the center of one of the most thickly populated 
sections of the United States; hence there was an unusual oppor- 
tunity for the spread of the insect by artificial means. In spite of 
the work that has been done and the observations that have been 
recorded it has remained until the last two years for a demonstra- 
tion to be made of- the manner by which this insect is spread, to the 
greatest extent, by natural means. 
MEANS BY WHICH INSECTS ARE SPREAD. 
One of the principal methods of insect locomotion and of spread- 
ing is by flying, and there is little chance of preventing the spread 
of a strong-flying introduced species which has become thoroughly 
established. The continued spread of the elm leaf-beetle and of the 
brown-tail moth illustrates how flying insects are dispersed. 
There is, however, another class of insects which does not spread 
by flying. Several distinct types exist, and among them may be 
mentioned such insects as the San Jose scale and other closely re- 
lated species. The structure of the females of this group is such 
that they remain fixed before becoming sexually mature; hence the 
distribution of the species is confined, so far as natural means is 
concerned, to the dissemination of the young, which have the ability 
to move about for a limited period. The adult insects are spread 
by artificial means on nursery stock and on living trees or shrubs that 
are shipped from one locality to another for planting or propagation. 
The brown-tail moth has also been distributed on nursery stock, but 
it is carried in this way while the small caterpillars are in the 
hibernating webs where they pass the winter. 
