204 Papers from the Department of Marine Biology, 



Late in the afternoon of July 5 the wind at Rebecca Shoal began to 

 shift eastward, being east-northeast at 5 p. m. and east by north at 

 9 h 45 m , blowing freshly. The last mosquito was taken at 8 p. m. Day- 

 light of July 6 still found the wind east by north and moderate. Two 

 mosquitoes were captured, one at 5 a. m. and the second at 8 h 27 m 

 a. m., the last for the day. These individuals were, no doubt, the 

 rear guard of those brought from Florida by the winds of the day pre- 

 ceding. 



No more mosquitoes appeared until July 8, when 4 were taken during 

 the forenoon; July 9 yielded 6 more, all Aedes niger. Since the wind 

 on July 7-8 and forenoon of July 9 was east that is, it was blowing 

 directly along the reef from Marquesas to Rebecca Shoal the infer- 

 ence is that the mosquitoes were carried by the light breeze from these 

 islands 24 miles away. Although there are extensive brackish swamps 

 on the Marquesas Keys, it was found, when we visited them on July 

 30, that most of the water had evaporated, leaving only heavy mud. 

 Rains had been infrequent during the preceding weeks with the 

 result that swamps, which during the rainy season give rise to multi- 

 tudes of mosquitoes, were during July unproductive. There were 

 many adult Aedes niger in the grass and among the mangrove trees, 

 however, and it was no doubt from their ranks that the few brought 

 on east winds to Rebecca Shoal were derived. 



It was hoped that another north wind would arise, so that the 

 striking migration observed on July 4 and 5 might be duplicated. 

 While this did not happen, I was fortunate enough to be on the station 

 during a period of southerly breezes which brought an even more 

 marked flight of mosquitoes. After several hours of calm on July 

 10, southeast squalls blew up late in the evening, lasting for two hours. 

 The wind then veered into the south and finally held west-southwest, 

 blowing freshly all night. At 5 h 30 m a. m. of July 11 the first mosquito 

 was captured; 32 more were added to the collection during the day, and 

 were well distributed as to time, 2 being caught at 7 h 30 m a. m. and 1 at 

 each of the following: 8 h 15 m , 8 h 30 m , 8 h 52 m , 8 h 56 m ,8 h 57 m , 9 h 07 m , 9 h 08 m , 

 9 h ll m , 9 h 16 m , 10 h ll m , 10 h 24 m , Il h 38 m , Il h 40 m , 12 h 05 ra , 12 h 10 m , 12 h 13 m , 

 12 h 15 m , I h 20 in , I h 22 m , I h 25 m , 3 h 30 m , 4 h 10 m , and 5 h 09 m ; between 6 h 30 m 

 and 7 h 30 m p.m. 7 more were taken, but none was noted after darkness 

 fell. 



The greater number rose only to the platform level, but 8 reached 

 the second story above, and 1 was caught by one of the assistant keepers 

 while painting the railing above the lantern at the very top of the sta- 

 tion, 65 feet above the water. In order to determine whether the 

 insects were numerous just above the surface of the sea, I stationed 

 myself on the boat-landing 8 feet from the water. One or two speci- 

 mens were caught here attempting to bite, but they seemed no more 

 abundant than at the level of the platform 30 feet above. 



