DISTANCE OF FLIGHT 273 



Neumann at Rio de Janeiro. They state that a draft is undoubtedly disagree- 

 able to calopus. On this account they searched for it in vain in exposed situa- 

 tions accessible to wind, as for example the Monte da Providencia within the city. 

 It would seem that the yellow-fever mosquito does not fly very far and the fact 

 that it is very rarely found away from houses supports this view. Carter points 

 out that it probably never flies high, and that it is found by preference in the 

 lower stories of houses. The same writer in 1904 suggested that the problem of 

 flight be investigated as of importance in determining the anchorage of vessels 

 in yellow-fever ports. He say on this point : 



" So far he knows of no direct observations on this subject, except those of 

 Goldberger at Tampico, and of Grubbs at Ship Island Quarantine. The latter 

 found Stegomyiffi aboard three vessels from Vera Cruz, two of which claim to 

 have lain a half mile from shore. He believed they came aboard at Vera Cruz. 

 The observations of Goldberger will be given later. 



" Although direct observations on this problem are few, yet there are certain 

 indirect ones, bearing, however, entirely on the aerial conveyance of the Stego- 

 myia infected with yellow fever. It is notorious that yellow fever is usually 

 conveyed but a short ways aerially, ' across the street,' or, more often ' to the 

 house in the rear,' which is about as far as it was expected to be thus conveyed. 

 This represents a maximum distance of about 75 yards. The two longest dis- 

 tances recorded in recent times of aerial conveyance, one of 225 meters (Melier) 

 and one of 76 fathoms — 456 feet (the writer) are entirely exceptional. So much 

 for the distances which the (infected) Stegomyia is conveyed — or rather usually 

 conveyed — aerially. 



" On the other hand it is known that vessels moored in certain districts of the 

 Havana harbor did not develop yellow fever aboard, except in those who had been 

 ashore, or unless they lay close to other vessels which were infected. This ex- 

 periment has been made on so large a scale — with so many vessels and for so 

 many years — that we must accept as a fact that an infected Stegomyia was not 

 conveyed aerially from the Havana shore to those vessels, or, allowing for errors, 

 was very rarely so conveyed. This distance which had been found safe was some- 

 thing over 200 fathoms — 1200 feet. The prevailing wind was generally slightly 

 on shore, but was not constantly blowing. Whether there is any difference in 

 the distance to which infected or non-infected mosquitos are conveyed, is, of 

 course, entirely a matter of surmise. There is no apparent reason why there 

 should be. Yet the infected Stegomyife have almost certainly become so in a 

 house ; and with their very domestic habits must be found out of doors, where 

 they would be subject to conveyance by the wind, in much smaller numbers than 

 the uninfected insects, and consequently a lesser number of them would be con- 

 veyed aerially. Observation is needed on this subject — the distance (across 

 water) that Stegomyia^ are aerially conveyed. 



" Goldberger, very ingeniously, suggests that on account of its diurnal flight, 

 the direction of the wind during the day only need be considered in estimating 

 this factor in their aerial conveyance, and states that at Tampico he failed to 

 find Stegomyise aboard vessels lying, for ten or fifteen days, about half a mile 

 from a place on shore where they were abundant, while numbers of Anopheles 

 albipes * and Culex pungens f were found. The wind was on shore during the 

 day and calm or off shore during the night. The importance of this point is 

 obvious, as on the coast, except when overborne by the trades, the direction of the 

 wind is very generally different by day and night." 



* Anopheles aliimanus Wied. 

 t Culex quinquefasciatits Say. 



