DEPARTMENT OF MARINE BIOLOGY. 169 



by the wind a minimum distance of 105 nautical miles from the region of 

 Cape Sable. Some of them may have traveled the 180 miles from Tampa 

 Bay; the direction of the wind would have made this possible. 



On July 6, when the wind had been blowing for 12 hours from the east, 

 only 2 mosquitoes were taken, both being 0. tceniorhynchus. These, as well as 

 the 4 captured on July 8 and the 6 on July 9, no doubt came from some key — 

 probably Marquesas— to the eastward of the Florida reef. They are known 

 to breed there. 



The second remarkable migration of mosquitoes occurred at Rebecca Shoal 

 on July 11, following a change of the wind on the 10th from east through 

 southeast to southwest. The first specimen was taken at d^ZO"" a. m., 2 more 

 at y'^SO'", another at 8''15'", and during the ensuing period until I'^SS"" p. m., 

 19 mosquitoes, one at a time. Between S^'SO'" and 5^09"" p. m., 3 more were 

 added, followed by the last 7 captured between G^^SO™ and 7 p. m. It is impor- 

 tant to record that the cessation of mosquito arrivals coincided with the dying 

 out of the wind at dusk. 34 specimens of 0. tceniorhynchus and 3 of 0. sol- 

 lidtans had been taken during the day on an actual area of the ocean's surface 

 only 40 feet square. It should be borne in mind, however, that the sense of 

 smell possessed by the mosquitoes undoubtedly increased the area within 

 which those taken may be regarded as having been distributed. 



The source of the mosquitoes reaching Rebecca Shoal on this south and 

 southwest wind must have been some portion of the Cuban coast. As stated 

 above, the shortest distance in this direction is 95 miles from Havana and the 

 longest 230 miles from Cape San Antonio on the southwest. 



My experiences at Rebecca Shoal on July 11 were supplemented by those of 

 Dr. A. G. Mayer and other observers at Loggerhead Key, 18 miles to the west- 

 ward. Under the same wind conditions Dr. Mayer notes that "mosquitoes 

 were noticed at about noon of July 11, and became a pest by night, so that we 

 were unable to lie on the sand at the northern end of the island. Many of 

 them were also found in the laboratory, and they were thick in the bushes 

 near the buildings and on the ocean about 300 feet from the shore on the west 

 side of the island. During the night of July 1 1-12 the wind veered to southeast 

 by east-southeast and the mosquitoes practically disappeared." All of the 

 22 specimens taken by Dr. Mayer on the above date proved to be 0. 

 tceniorhynchus. 



The last hours of the southerly winds brought 7 more of the same species 

 to Rebecca Shoal on the forenoon of July 12. On the night of July 12-13 the 

 wind veered into the east, blowing steadily and strongly from east by south 

 for the remaining 6 days of my stay there. That no more mosquitoes were 

 taken may be accounted for by the fact that any leaving Marquesas must 

 have been carried a few points to the northward. It is unhkely, moreover, 

 owing to the force of the wind, that insects could have alighted, except in the 

 lee of the station. 



Of paramount interest are the observations made at Rebecca Shoal concern- 

 ing the forced migration of the common house-fly, Musca domestica. During 

 the light east -udnds from 3 to 5 specimens were taken per day. Therefore 

 the capture of 25 on July 6, following a quick change of the wind from north to 

 east was very striking. The inference is that they were brought from points 

 eastward on the reef or possibly from the southern extremity of Florida. On 

 July 7 the numbers of Musca domestica visiting the station dropped to 5, the 

 normal for light east winds ; 5 more were taken on the 8th and 3 on the 9th. It 

 is interesting to note that none appeared on the 10th while the wind was chang- 

 ing to south. Along with the 37 mosquitoes, 18 house-flies arrived from Cuba 

 on July 1 1 . Although the wind on the 12th was south-southeast, 7 were taken 



