THE GIPSY MOTH ON CRAKBERRY BOGS. 
velocity was recorded at a point about 25 feet above the bog level by 
a Eobinson cup anemometer. The direction of the wind was also 
noted at hourly intervals during the day. The traps made it possi- 
ble to count the caterpillars falling upon a known area, under given 
conditions, and at different locations on the bog, and to compare 
these records from year to year. 
DESCRIPTION OF TRAPS. 
The traps used by Burgess and Collins in previous wind disper- 
sion experiments were constructed of 1-inch mesh wire poultry fenc- 
ing, erected in a vertical position, and made in several sizes, their 
principal object being to demonstrate the certainty of wind dis- 
persion. 
A study of the results of these experiments indicates that quite a 
percentage of the caterpillars, particularly when the wind attained 
a velocity of 20 miles or more per hour, were blown through the 
meshes of the wire, notwithstanding the fact that the wire was well 
covered with commercial sticky tree-banding material. Eight hori- 
zontal traps having a solid surface were used in the bog experiments, 
numbered 1, 2, 3, 4, 7, 8, 9, and 12, and two vertical traps numbered 
10 and 11. (Fig. 1.) 
The horizontal traps were 20 feet long and 2 feet 8 inches wide, 
outside measurement. These dimensions were adopted for two prin- 
cipal reasons: First, to facilitate inspection of the surface, and, sec- 
ond, to reduce the danger of wind damage. For convenience in 
handling, they were made in two sections, each 10 feet long. The 
framework was made of wood 1 inch thick and 2 inches wide with 
a strip through the center to prevent the covering from sagging. 
(PI. II, Fig. 1.) 
Cotton cloth was first used for covering the frame, but this was 
not satisfactory, owing to its tendency to sag and hold rain water. 
Wall board was substituted, and proved very effective. Support- 
ing stakes were driven into the bog at such height that when the 
frame was nailed to them, the two sections sloped from the center 
toward either end, in order to shed all moisture. (PI. II, Fig. 2.) 
The upper surface of the wall board was given a coat of outside 
white paint, which helped materially in distinguishing the small 
gipsy moth larvae from the myriad of midges and other insects 
that are caught upon the trap. After the paint was dry the surface 
was marked off into 64 oblong sections 8 inches wide and 15 inches 
long. This made it possible to be sure that the whole surface was 
inspected and saved considerable time in making collections of 
larvae that were caught on the trap. 
