OTHER ANIMALS 659 



the water when disturbed. The manner in which the pupa rises to 

 the surface without effort demonstrates that its weight is less than 

 that of the water. The length of the pupal stage is a matter of 

 about two days. 



The Yellow-Fever Mosquito, Stegomyia Fasciata. This mos- 

 quito is the notorious yellow-fever species of Cuba. Just how or 

 when it comes to these Islands is unknown. Dr. Howard under 

 date of January 27, 1903, writes: The two species of Stegomyia 

 occur throughout the East Indies. Prof. V. L. Kellogg of Stanford 

 University, in writing of his trip to the Samoan Islands a year ago 

 says: I am interested to learn that your day mosquito is the yel- 

 low-fever chap, Stegomyia fasciata. That is just what I found the 

 Samoan mosquito to be. * * * This is the abundant Samoan 

 mosquito and the one which presumably disseminates elephantiasis. 

 The dissemination of yellow-fever by the mosquito is not a new 

 idea. Dr. Carlos Finlay of Havana, Cuba, was of the opinion, as 

 early, as 1881, that this disease was conveyed by this pest. This 

 theory was proved a fact by a commission oif surgeons of the United 

 States Army by demonstrations made in Cuba in 1901. They 

 proved beyond all doubt that this species, Stegomyia fasciata, was a 

 conveyor and perhaps the only conveyor of this dreaded disease. 



The propagation of the disease depends upon the introduction 

 of an infected individual to a locality where this mosquito is found, 

 at a season of the year when it is active. Owing to the short period 

 of incubation (five days or less), the brief duration of the disease, 

 and especially of the period during which the infectious agent 

 (germ) is found in the blood (three days), it is evident that ships 

 sailing from infected ports, upon which cases of yellow-fever de- 

 velop, are not likely to introduce the disease to distant sea-ports. 

 The continuance of an epidemic on shipboard as on land, must 

 depend upon the presence of infected mosquitoes and of non- 

 immune individuals. Under these conditions we can readily un- 

 derstand why the cHsease should not be carried from the West 

 Indies or from South America to the Mediterranean, to the east 

 coast of Africa, or to Asiatic seaport cities. On the other hand, if 

 the disease could be transmitted by infected clothing, bedding, etc., 

 there seems no good reason why it should not have been carried to 

 these distant localities long ago. 



The yellow-fever mosquito is well named a towri species. It 

 breeds almost exclusively about dwellings, and authorities state that 

 it is seldom found far outside city limits unless in the vicinity of 

 dwellings. The female will invariably choose small collections of 

 clear water for depositing her eggs. The eggs are laid singly on 

 or near the water and if not on the water may remain dormant for 

 a long time until washed into the water or, as in the case of a rain- 

 barrel, until a shower brings the water to their level. Attention to 

 the artificial collections of water about dwellings will be the prin- 

 cipal factor in reducing the numbers of this species. 



The Forest Mosquito, Stegomyia Scutellaris. This species and 

 the yellow-fever mosquito are known locally as the day mosquitoes. 



