MOSQUITOES AND VESSELS 351 



amined to ascertain if mosquitoes were present on board, and, if present, their 

 variety, where and when they came aboard, and under what conditions. 



" Gulf Quarantine Station is an especially good point for these observations, 

 from the fact that it is 10 miles from the mainland, and because vessels bound 

 here do not pass near land, and so but rarely take on mosquitoes en route, and 

 even these, as will be seen, are always the marsh-bred varieties of Culex. Be- 

 sides, the examination of at least a thousand mosquitoes on Ship Island has 

 convinced me that there are no Stegomyia here. 



" Each vessel inspected was carefully searched, the inspector being armed 

 with a cyanide killing bottle, and in addition the captain was asked the following 

 questions : 



" 1. Were there any mosquitoes on board on your outward voyage, consisting 

 of days ? 



" 2. If so, did they come aboard before departure from home port or at sea, 

 and under what circumstances ? 



" 3. Were there any mosquitoes on board at your destination or on homeward 

 voyage ? 



" 4. If in port — 



(a) How far were you from shore ? 



(b) Prevailing wind and weather? 



" 5. If on homeward voyage (consisting of days) — 



(a) Were they from port ? 



(b) Did they come aboard at sea, on what day, and how far were vou from 

 land? 



(c) Were there wigglers in any of your tanks at any time ? 



" During the five months from June 1 to November 1 observations were made 

 on 82 vessels, all arriving from ports where the Stegomyia is believed to exist 

 in quantities. Of these 78 were sailing vessels and 4 were steamers. 



" Of these 83 vessels, 65 claimed to have had no mosquitoes aboard at any 

 time during the voyage or at port of departure, and their absence having been 

 confirmed by search, we can dismiss them from consideration and pass to the 

 remaining 17. 



'' Five of these had mosquitoes on board at their ports of departure, 2 being 

 rid of them as soon as they were well at sea, while 3 others carried them two days 

 and were then no more troubled, except one schooner on which they reappeared 

 in quantities five days before she reached port, when she was 20 miles from shore. 



" Mne sailing vessels, having no mosquitoes on board before sailing, had them 

 appear at sea, in one case from the water casks in which the captain found larvas. 

 But in the other cases they doubtless came from land which was at the time 

 distant — 20 miles in one case, 15 miles in three cases, 10 miles in one case, and 

 2 miles in the last two instances. In all these vessels the mosquitoes found on 

 board on arrival at this station were the common varieties of Culex, there being 

 no Anopheles or Stegomyia among them. 



" Stegomyia fasciata were found on board and were identified in the remain- 

 ing three cases, as follows : 



" The schooner Susie B. Dantzler arrived from Vera Cruz, Mexico, on July 

 16, 1902, after a voyage of fifteen days. The captain stated that mosquitoes 

 came aboard in large quantities at Vera Cruz, although he lay a half mile from 

 shore and there were variable winds with squalls and rain all the time. The 

 number of the insects decreased on the voyage but were always in evidence, and 

 we caught four or five of them here. No larvae were found in any of the tanks, 

 and as the captain had repeatedly examined them without result in his efforts 

 to be rid of the mosquitoes, I believe the insects found on board here came all 

 the way from Vera Cruz. 



