DISPEKSION OF GIPSY-MOTH LARV^J BY THE WIND. 11 



In all 96 larvae were trapped during the season, most of which 

 were removed on days when the wind blew from the west, southwest, 

 or northwest. The largest catch was removed May 21, at which time 

 the wind blew from the northeast and southeast, but it was evident 

 that most of the larvae were caught May 20 in the afternoon, as the 

 screen was not examined during that period. There was less source 

 of spread from the northeast and southeast along the ocean shore 

 than from the westward points. On May 21 the temperature ranged 

 from 53° to 60° F., at which time there was reasonable activity among 

 the caterpillars. 



One should not fail to note that spread was secured from all direc- 

 tions from which the wind blew except from the east, and the in- 

 festation at this point Was almost obliterated. No north winds 

 were noted during the hourly observation periods. 



SCREEN EXPERIMENT CONDUCTED ON PLUM ISLAND, MASS., IN 1914. 



April 14, 1914, a screen (PI. Ill, fig. 2) was erected on the edge 

 of the marsh near the Merrimac River. It was of the same size and 

 proportions as that erected 1 mile farther north, at Salisbury Beach. 

 The shrubbery, composed mostly of beach plum, bayberry, wild rose, 

 sumac, poplar, and willow, on the north end of the island, was ex- 

 amined for egg clusters and these were creosoted. This practically 

 obliterated the source of infestation to the eastward of the screen. 



The location of the screen (PI. Ill, fig. 2) was such that it was 2 

 miles from infested woodlands across the marshes and Merrimac 

 River to the northwest, west, and southwest. Frequent examina- 

 tions made it possible to determine the direction from which all the 

 caterpillars came. It is not supposed that all the caterpillars caught 

 during the time west winds prevailed came from the nearest infesta- 

 tions (2 miles), but in some instances 5 miles or more. There was, 

 however, a small infestation on a few roadside willows 1 mile to the 

 southwest, but these were so thoroughly cleaned and tanglefooted 

 in the spring that no caterpillars could be found on them during the 

 dispersion season. The woodland infestation was 1 mile beyond 

 this, totaling 2 miles from the screen. 



Mr. C. E. Hood attended the screen, making three or four exami- 

 nations for larvae daily from May 10 to Juno 13. The temperature, 

 wind direction, and wind velocity wero recorded hourly each day 

 from 8 a. in. to 5 p. in., inclusive. 



