DISTANCE OF FLIGHT 341 
habits of these mosquitoes is essential. These are discussed in another part of 
this work (p. 146). 
Dr. Smith’s method of investigating the migrations of the salt-marsh mos- 
quitoes was to station observers on the marshes before the larvee matured. Care- 
ful search was made for several miles back in order to prove that none of these 
mosquitoes were there. Then the appearance of the first brood of adults on the 
salt marshes was noted early in the season. They were watched for a day or two 
slowly advancing until they reached the first ridge of mountains. A second 
brood, maturing during the last days of June, 1903, was watched in the same 
way, and the early days of July brought inland the greatest swarm of mos- 
quitoes he had even seen. They reached New Brunswick July 2d and included 
the three species above mentioned. One of.Dr. Smith’s assistants, Mr. Viereck, 
was, at the same time, observing at Cape May, and watched the peninsula filling 
with sollicitans bred at the shore. Away from the shore he could not find the 
larvee, while the adults swarmed. He noted that after continuous south wind 
the marshes became practically free from mosquitoes, whereas a few days later 
blood-filled specimens with developing or developed ovaries returned to the 
marshes from the upland. This, he thought, was a return migration for ovi- 
position, all the specimens being worn. Dr. Smith now has no hesitation in 
stating that these salt-marsh species may migrate inland for 40 miles. 
Flights to sea are apparently not infrequent, although they have been but 
seldom recorded. According to Dr. Smith salt-marsh mosquitoes are not un- 
common 5 miles out, and have been reported 15 miles out. 
Dr. H. R. Carter, discussing this subject in 1904, thinks that salt-marsh mos- 
quitoes are “ quite frequently carried considerably over a mile by light, steady 
breezes, long continued.” THe records the occurrence of a great swarm of salt- 
marsh mosquitoes in the Gulf of Mexico, many miles from land, as follows: 
“The writer has personal knowledge of the flights of myriads of mosquitos 
(Culex solicitans as he remembers) which were carried by wind fifteen or 
eighteen miles from the Louisiana marshes across Chandeleur Sound to vessels 
in the sound and to Chandeleur Island. In both cases the wind had blown 
moderately and steadily for two or three days from the marshes.” 
Dr. Alfred G. Mayer, the Director of the Marine Laboratory of the Carnegie 
Institution at Tortugas, Florida, found that the Tortugas Islands are occasion- 
ally invaded by swarms of migratory mosquitoes. He investigated the conditions 
on the seven islands carefully in 1908 with reference to possible breeding-places 
of mosquitoes and he describes these as follows: 
“The seven Islands of the Dry Tortugas, Florida, are composed exclusively 
of wave-worn and wind-blown fragments of shells and other calcareous remnants 
of marine animals and plants which once lived in the water surrounding the 
keys. These particles form a loose, coarse, soil which does not permit the 
growth of mangroves, and which is so porous that no puddles or standing pools 
of water are to be seen even immediately after the most copious tropical rains. 
There are no enclosed lagoons or areas of relatively stagnant salt-water as in 
many other keys of the Florida-Bahama region, and all parts of the Islands are 
dry and elevated from 3 to 9 feet above sea-level. The islands are covered with 
