On July 13 the wind, east by south early in the morning, finally settled into a strong and steady blow from due east and continued 80 through the next 6 days. A single mosquito taken on the morning of July 13 was the last which appeared during my stay at the lighthouse. As Smith has shown, mosquitoes do not rise from the ground while strong winds are blowing. Had any been carried to the station it is improbable that they could have made a landing even on the lee side in the gale.
Very important, as supplementing my experiences at Rebecca Shoal, are observations made at Loggerhead Key by Dr. A. G. Mayer and other investigators. On July 11 they noted, under similar wind con ditions to those at Rebecca Shoal, an unusual abundance of mosquitoes and preserved 22 specimens, which proved to be of the same species, A. niger. Dr. Mayer made the following record: "On the night of July 10, at about 8 p. m., there was a sudden squall with rain from the southeast. By the morning of July 11 the wind was south to south-southwest, blowing in a gentle south-southwest breeze all day. Mos quitoes were noticed at about noon of July 11, and became a pest by night, so that we were unable to lie on the sand, as is our custom, at the southern end of the island. Many of them were also found in the laboratory, and they were thick in the bushes near the buildings and over the ocean about 300 feet from shore on the west side of the island. During the night of July 11 and 12 the wind veered to southeast to east-southeast, and the mosquitoes practically disappeared." Thus it appears that the migration of July 11, occurring simultane ously at Rebecca Shoal and Loggerhead Key, presented a front of at least 20 miles. The individuals which actually alighted upon the station were, of course, only a small percentage of those which crossed the open sea within the visual radius of 13 miles; only those which came very close could have been attracted by any slight odors emanating from the lighthouse. Although Loggerhead Key is three-fourths of a mile long and hence much larger than Rebecca Shoal station, it still represents a small area on the surface of the sea. From these data one hesitates to compute the possible numbers of mosquitoes that were carried out to sea by the wind blowing from the Cuban coast.
On July 18, I was transferred from Rebecca Shoal to the Tortugas, where observations were continued. The wind held in the east for the 10 days of my stay there, so that no opportunity arose to witness another mosquito migration. Attention was turned toward a deter mination of the numbers and species of the mosquitoes still present on the islands, and their possible breeding-places.
As stated by Dr. Mayer, the veering of the wind on the night of July 11-12 caused a marked decrease in the numbers of mosquitoes encountered in the vicinity of the laboratory; still it was possible 10 days later to attract considerable numbers of Aeries niger by stationing one's self quietly in the shade near the bay cedar bushes. On July 22 mosquitoes in one of the laboratories were so numerous that 4 were taken in one sweep of the net. Again on July 23, in the half hour just preceding darkness, 11 specimens were caught.
Since there are no swamps on the small sandy keys, the only breeding places for mosquitoes are such receptacles as may be maintained or left by man. Examination showed that no lame were present in the fresh-water storage reservoirs at the laboratory or at the Loggerhead light-station. It was thought likely that mosquitoes might be breeding in cans thrown upon a waste pile among the bay cedar bushes. On investigation many were found that contained rain-water but no larvae. In short, not a single larva was found on Loggerhead Key during my visit. Nevertheless, one small batch had, earlier in the season, ma tured in a shallow pool on a cement floor beneath the refrigerator, and the possibility is not excluded that Stegomyia calopus may have been breeding there late in July; several specimens of this species were cap tured about the laboratory. But that Aeries niger or sollicitans were breeding at that time is extremely doubtful, for both require brackish water for their development, and all the receptacles contained only fresh water. Not only in the vicinity of the laboratory was it easy to obtain specimens; they were distributed over the entire key. In the early morning, afternoon, and evening A. niger could be attracted from the grass and bay cedar bushes.