168 



CARNEGIE INSTITUTION OF WASHINGTON. 



Mosquitoes found in 23 days at Rebecca Shoal lighthouse. 



Date. 



June 26-30 



July 1 



July 2 



July 3 



July 4 



July 5 



July 6 



July? 



Julys 



Wind. 



E., light 



Do 



ENE., Ught 



N. at 5 a. m 



NE. at 10 a. m 



N. at 12 noon 



N., freshening in p. m 



N., light in a. m 



N. by W., fresh in p. m 



N., light in a. m 



ENE. to E. by N., mod. in 



p. m. 

 ESE. to NE., fresh in p. m. . 

 E., light 



Do 



No. 



Date. 



July 9.. 

 July 10, 



July 11, 



July 12. 

 July 13. 

 July 14. 

 July 15. 

 July 16. 

 July 17. 

 July 18. 



Wind. 



E. to NE., light 



E., 5 a. m 



Calm, 4 p. m 



SE., S^^SO" p. m 



WSW., fresh, 5 a. m. 

 SW., light, 5p.m. . . 

 SW., calm, 9 p. m. . . 

 ESE., fresh to strong 

 E. by S., strong 



Do. 



Do. 



Do. 



Do. 



Do. 



Total 



No. 



37 



7* 



1 























83 



*In forenoon. 



On July 1, during a period of east winds, a single mosquito was caught. 

 Not until the morning of July 4, after the wind had been blowing lightly 

 but steadily from the north for 27 hours, did another appear at the station; 

 1 was taken at 8 a. m. and 3 more between 6 and T'^SO"' p. m, 



July 5 proved to be one of the days on which mosquitoes were sufficiently 

 numerous to be distinctly in evidence by virtue of their humming and biting. 

 The first specimen was taken at 4^30"" a. m. Between 5''30'" and S'^IS" a. m. 

 13 more were captured. During the rest of the day individuals taken at 8''36'°, 

 9h20m^ 11^45"^ a. m. and 12i'02™, 41^30"^, 7, and S^OG'" p. m. brought the total to 

 21 mosquitoes. The moderate wind which had blown steadily from the north 

 throughout the night of July 4-5 continued so until 5 p. m., when it veered into 

 the east and freshened. It is important to note that, following this change, 

 only 2 mosquitoes were taken on July 6, both of these early in the day. 



Judging from this sudden and marked increase in the number of mosquitoes 

 visiting the lighthouse following a change of 90° or more in the direction of 

 the wind, as well as the fact that a period of at least 27 hours elapsed between 

 the time that this change began and the arrival of the first mosquitoes at 

 Rebecca Shoal (5 a. m. July 3 to 8 a. m. July 4), it seems a fair conclusion 

 that they must have been carried from some point on the west coast of Florida. 

 Furthermore, all of the 25 specimens were salt-marsh mosquitoes; that is, the 

 larvae have been found only in the strongly brackish waters of coastal marshes. 

 Of those taken on July 4 a single one belonged to the species Ochlerotatus 

 sollicitans Walker, while the other 3 and the 21 taken on July 5 were 0. tcenio- 

 rhynchus Wiedemann. As Dr. J. B. Smith and his assistants so clearly 

 demonstrated in New Jersey during their investigations of 1902-04, 0. sollici- 

 tans has the remarkable habit of migrating inland in immense swarms for 

 distances of 30 miles or more in search of food. Of the second species as 

 observed in his State, Dr. Smith says: "Culex tceniorhynchus develops with 

 cantator and sollicitans under the same conditions and migrates with them; 

 but it does not fly so far and is always so much less abundant that it requires 

 no special account here." It therefore appears that the southern representa- 

 tives of these two species have similar migratory habits. But instead of being 

 found 15 miles out at sea, as Dr. Smith mentions their having been seen in 

 the north, our observations indicate that large numbers of them are carried 



