DISPERSION OF GIPSY-MOTH LARVE BY THE WIND. 



13 



receive the full force of the northwest, west, and southwest winds 

 directly from the mainland. This island is composed mostly of bare 

 rock, with small patches of soil. There is little favorable vegetation 

 for gipsy-moth larvae, and three careful examinations made in the 

 spring of 1914 revealed no egg clusters. 



Four hundred and fifty square feet of wire screen was used, and 

 an extra screen was made of cotton cloth tacked to a frame 40 feet 

 long and 3 feet wide, and tanglefoot applied. It was anchored at 

 an incline on the rocks, facing the west. 



On this island there is one cottage which afforded quarters for 

 Mr. Harry L. Blaisdell, who was in constant attendance at the 

 screen (PI. IV, fig. 1). Arrangements were also made with the 

 United States Life-Saving Service for transportation to and from the 

 islands on their regular trips to Portsmouth, N. H. Mr. Blaisdell 

 recorded the weather conditions hourly from 8 a. m. to 5 p. m., using 

 a compass, thermometer, and hand anemometer. He also examined 

 the screens continuously and made careful notes on the time and 

 wind conditions when each caterpillar was caught, which made it 

 possible to determine the source from which it came. Practically 

 all the larvae found on the screens were alive, and in most cases they 

 were removed very soon after entanglement. 



Table V.- — Number of caterpillars caught at Lunging Island, Isles of Shoals, N. H., in 

 1914, with direction and distance from which they came. 



Date. 



Other islands 

 of the Isles 



of Shoals, E., 

 SE., BE., 



and S.,i and 

 \ mile. 



Kittery, Me., 

 NW., 7 miles. 



Wallis Sands 

 and Rye, 



N. H*., 



TOW., 6 



miles. 



Rye Ledge 



and Littlo 



Boars Head, 



N. H.,W., 



7 miles. 



Seabrook, 

 New Hamp- 

 shire, and 

 Massachu- 

 setts line, 

 WSW.,11 

 miles. 



Plum Island 



(north end), 



Mass., SW., 



13J miles. 



1914. 

 May 20 



6 

 6 

 1 



1 











MaV 21 























May 2.'5 . 





8 



20 



3 







May 24 . 







1 





May 20. . 



7 

 2 

 1 

 1 

 1 







9 



May 26 





































j 











Total 



25 



1 



28 



3 



1 



9 



Sixty-seven Larvae were, removed from the screen and cotton cloth 

 between May 20 and June 2. The wind data given in the table were 

 taken on the island, but comparison vva,s also made, with the records 

 taken a1 Plum [sland, Mass., \'.\h miles lo the southwest. Tt was 



thought thai the air currents on the shore of the mainland where 

 mosi of the small larvae were picked up would l>e much changed from 

 their course before reaching the islands, but only slight differences 

 were noted by the two observers during the period. 



