16 THE DISPERSION OF THE GIPSY MOTH. 
colonies which are found long distances from any badly infested area. 
Isolated colonies have been usually so far away from infestations that 
it would have been practically impossible for small females to have 
covered the distance by flying. 
SUGGESTIONS CONCERNING THE SPREAD OE LARViE BY THE 
WIND. 
In the fall of 1909 Prof. E. D. Sanderson, who was then ento- 
mologist to the Xew Hampshire Agricultural Experiment Station, 
and who was deeply interested in the work of suppressing the 'gipsy 
moth, suggested that the caterpillars of this insect might be car- 
ried by natural means, and later he wrote to Dr. L. O. Howard, 
Chief of the Bureau of Entomology, calling attention to an article 
in the Standard Natural History relative to the peculiar hairs on 
the young caterpillars and suggesting that they might assist the 
larvae in being carried by the wind. xVn examination of the liter- 
ature showed that the matter had been mentioned by Forbush and 
Fernald in 1896 and that the hairs had been described by Wachtl 
and Kornauth in a publication relating to experiments in the forests 
of Austria in 1893. This paper deals principally with hairs of 
peculiar structure which are found in the first-stage larva? of the 
nun moth {Psilura monacha L.) and states that similar hairs are 
found on the first-stage larva? of Porthetria clispar. 
These hairs are not present on the caterpillars in the later stages, 
and as they are provided near the base with .a globular enlargement, 
which the authors believed to be filled with air or gas, they were 
called aerostatic hairs and the globes aerophores. They state that 
the first -stage nun larva? are carried long distances by the wind, 
and one might assume that the same is true of the gipsy-moth larva?, 
as they are provided with similar hairs. 
A microscopic examination of one of these first-stage caterpillars 
shows that two kinds of hairs arise from the tubercles which are 
arranged in rows on the bodv. Onlv a few slender acuminate hairs, 
some of which are nearly half as long as the caterpillar, arise from 
each tubercle (PI. V), but many short hairs are present which have 
a small globular swelling near the base. Whether these aerophores 
actually aid in making the caterpillars more buoyant, as is sug- 
gested by the authors above mentioned, is not positively known, 
but it was of great importance to know whether dispersion is actually 
brought about by means of the small larva? drifting in the wind. 
EXPERIMENTAL WORK. 
In the spring of 1910 a preliminary experiment was tried in the 
laboratory by releasing caterpillars, which had been encouraged to 
spin as much silk as possible, in front of an electric fan. Although 
