12 



BULLETIN" 273, U. S. DEPAETMENT OF AGEICULTUEE. 



Table IV. — Dates and numbers of newly hatched caterpillars caught on screen, with tem- 

 peratures, direction of wind, and velocity of wind at Plum Island, Mass., in 1914. 



Date and time removed. 



Number of 



caterpillars 



caught. 



Maximum 

 tempera- 

 ture. 



Minimum, 

 tempera- 

 ture. 



Average between 9 a. m. 

 and 5 p. m. 



Prevailing "Wind veloc- 

 v.ind direc- ity, in miles 

 tion. per hour. 



May 20, a. m. and p. m 



May 21, a. m 



May 22, a. m 



May 23, a. m. and p. m 

 May 24, a. m. and p. m 

 May 25, a. m. and p. m 



May 26, p. m 



May 27, p. m 



May 28, p. m 



Total 



3 F. 



"\V. and >TW. 

 NE. toSE.. 

 E. and SE.. 



W 



W 



S"W 



SW. and W, 



W. toS 



NW 



2 to 6 

 7 to 11 

 2 to 10 



10 to 23 



11 to 16 



12 to 21 

 7 to 20 

 4 to 12 



11 to 20 



A total of 42 caterpillars were removed from this trap between 

 May 20 and May 28 — a very short season in comparison to the 

 records at Salisbury Beach in 1913. Five of these larvae were 

 blown on the screen by winds from the east and south, while the 

 remaining 37 came with the winds from the west. Larvae were 

 caught during the morning of May 20, when the velocity of the wind 

 for that period ranged from 2 to 4 miles per hour, and on the follow- 

 ing day, when the temperature ranged from 53° to 60° F. 



SCREEN EXPERIMENT ON ISLES OF SHOALS, N. H. 



The Isles of Shoals (PL II), located 6 miles off the coast of New 

 Hampshire and Maine, was selected as an ideal place in which to 

 establish a trap for tests in long-distance spread. An elevated spot 

 on Appledore Island was chosen and a screen erected in April, 1913. 

 It was not known at that time that Appledore, comprising about 

 100 acres, was infested, but subsequent scouting in the summer 

 showed that this was the case. This island contains a varied growth 

 of low shrubbery, some of which is very favorable food for gipsy- 

 moth larvae, but the infestations were slight and covered small areas 

 well scattered over the territory. 



The screen was examined at intervals during that year from 

 May 1 to June 3 and 14 first-stage larvas were removed during that 

 period. Some of these larvae were alive on removal and were taken 

 on days when the wind blew directly from the mainland, which 

 indicated that many of them came from that source, but there was 

 room for question because the island on which the screen was located 

 in 1913 was later found infested. 



To ehminate any possibility of error in drawing conclusions another 

 island in this group, namely, Lunging, was selected for the experi- 

 ment in 1914. It is the most western of the isles and located so as to 



