THE GIPSY MOTH O^T CRa:^v"BERRY BOGS. 5 



velocitv was recorded at a point about '2b feet above the bog level by 

 a Robinson 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, imder 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 conmiercial 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 coverino- 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. (PL 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 larvffi 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 6-4 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 

 larva^ that were caught on the trap. 



