SPREAD TO NEW HABITATS 347 



In regard to steamsliips the same general facts hold. Mr. Busck has found 

 the yellow-fever mosquito on a steamer a day out from Jamaica, and he also 

 found it on board a Ward Line steamer in New York harbor. 



An excellent and suggestive paper on " Fruit Vessels, Mosquitoes and Yellow 

 Fever," was read before the Louisiana State Medical Society at New Orleans, 

 April 28, 1903, by Dr. Edmond Souchon, then president of the Louisiana State 

 Board of Health, and afterwards printed in the Journal of the American Medical 

 Association for June 13, 1903. Careful collections were made of the mosquitoes 

 arriving at New Orleans on board fruit vessels from Central American ports, 

 and these mosquitoes were determined in Washington at the Bureau of Ento- 

 mology. This paper, while indicating a great improvement over old conditions, 

 still, at the same time, showed how in previous years yellow fever had been 

 brought to New Orleans. 



The habit of Aedes calopus of seeking dark and protected places for hiding is 

 well known to ever}^one who has observed it. It will crawl into pockets, under 

 coat lapels, and under tumed-up trouser-ends, or it will hide in the folds of 

 garments hung in closets or upon the walls of a bedroom. Having these habits, 

 it is extremely liable, as Finlay already pointed out in 1881, to be transported 

 from one place to another in trunks. Garments folded in New Orleans and 

 packed loosely into a trunk may give out calopus hundreds of miles away. 



The gradual spread of the yellow-fever mosquito from lower altitudes to 

 higher ones in Mexico has been pointed out in the general consideration of the 

 habits of this insect, but it should be here stated that while this species breeds 

 naturally throughout the moist tropical regions near the Gulf of Mexico and 

 near the Pacific, its carriage to higher altitudes on the railroads running up 

 from Tampico and Vera Cruz is an almost daily occurrence. Through this 

 constant carriage on railway trains the species has become established at higher 

 altitudes where the conditions are suitable. Thus, at Cordoba it established 

 itself at first in the immediate vicinity of the railway station and gradually 

 spread upward from this center year after year until now it may be found breed- 

 ing in the center of the town, at a considerable distance from the station. The 

 same thing occurred still higher, at Orizaba (4200 feet). It has established 

 itself at Carasal on the Inter-Oceanic Eailway. It also occurs at points on the 

 railway from Tampico to Monterey (1600 feet) and it has been found in the 

 summer time at Saltillo — much higher than Monterey. It is doubtful whether, 

 had the railroads not been constructed, the yellow-fever mosquito would have 

 ever become established at many of these elevated inland localities. 



Mr. C. P. Lounsbury, government entomologist of the Cape of Good Hope, is 

 authority for the statement that the railroads in Cape Colony have been re- 

 sponsible for taking mosquitoes to many inland towns which before the introduc- 

 tion of train service were quite free from this pest. 



Skuse, writing of Culex quinquefasciatus, considers that it was introduced into 

 Australia from Europe by sailing vessels and says : " As the railway lines ex- 

 tend so this mosquito reaches portions of the country often hitherto exempt from 

 it, and it has been, and is being, communicated to other places along the coasts 

 by water traffic " (Proc. Linn. Soc. N. S. W., ser. 2, vol. 3, 1889, p. 1718). 



