DISPEESION OF GIPSY-MOTH LARVAE BY THE WIND. 15 
secured on those at Hillsboro and Troy, N. H., the infestations in 
the neighborhood of which were fewer and at longer distances. 
In 1912 several large gipsy-moth colonies were found in Andover 
and Henniker, N. H. On Beech Hill, Andover, about one-third of a 
mile from where the screen was erected, over 30,000 larvae were 
destroyed in the summer of 1912. This colony and surroundings 
were carefully treated, so that the infestation was nearly extermi- 
nated in 1913 and 1914. All the smaller colonies found in the town 
also received thorough treatment. Similar conditions prevailed in 
Henniker. 
The screens were examined at periods during the dispersion season 
of 1913 and 1914. No positive results were secured during the first 
year, but one living larva was removed from the Andover screen 
May 27, 1914, at 2 p. m. 
May 26, 1914, a dead larva was removed from the Henniker screen 
and a living specimen June 13, together with the molted skin of a 
second-stage larva. It is difficult to state from which direction the 
first larva was blown, but the second came from the northwest or 
west as the wind blew from those directions during the two days 
previous. 
The 3 first-stage larvae caught on the Andover and Henniker 
screens in 1914 proved conclusively that the dispersion among the 
hills is brought about most extensively by the wind. This is more 
emphatic when one considers the small air space covered by these 
traps and the small sources of infestation in these localities. 
ALTITUDE EXPERIMENT WITH AVIATION OF SMALL CATERPILLARS. 
At the close of the season's work in 1913, after securing some fair 
records on the distance that larvae are borne by the wind, it seemed 
advisable to get? data on the possible altitude they reach during their 
transportation. After numerous inquiries and investigation a suit- 
able place for such an experiment was found in Merrimac, Mass. 
(PI. VII). This consisted of the standpipe (PI. V, fig. 1) for the stor- 
age and pressure of the town water. It is located on a small hill 240 
feet above sea level, and permission to erect a small wire screen on 
the top of the tank was obtained from the selectmen of the town. 
The tank was 55 feet high from the level of the summit of the hill 
and a screen of f -inch mesh poultry wire was stapled to upright 2 by 4 
posts 5 feet long. The top selvage of the wire (PI. V, fig. 2) was 5 
feet above the top of the tank, totaling 60 feet above the ground. 
The screen was 36 feet long and contained 144 square feet, while the 
tank was 40 feet in diameter, allowing ample space for the examiner 
to get around the ends. It was set up so that the sides faced the east 
and west. 
