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 larvae 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 solUcitans bred at the shore. Away from the shore he could not find the 

 larvse, 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." He 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 



