SPREAD TO NEW HABITATS 347 
In regard to steamships 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 18, 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 Aédes calopus of seeking dark and protected places for hiding is 
well known to everyone who has observed it. It will crawl into pockets, under 
coat lapels, and under turned-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 Railway. 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. 8. W., ser. 2, vol. 3, 1889, p. 1718). 
