3o8 



The Two-winged Flies 



wide-spread and serious human diseases. The role played by mosquitoes 

 in the breeding and dissemination of the microscopic germs of malaria has 

 been so well exploited in news])apers and magazines that, although a matter 

 of comparatively recent determination, it is already common knowledge, at 

 least in its more general outline. For a somewhat detailed account of the 

 etiology of the diseases known to be disseminated by mosquitoes, including 

 the exact relation of the mosquito host to the disease-germs, see Chapter 

 XVIII of this book. It is sufficient to say here that the malarial germs seem 

 to live parasitically in and be disseminated by the various species of Ano- 

 pheles only, the yellow-fever germs only by the species Stegomyia jascialu, and 

 the minute worms of filariasis by the same species and two or three tropical 

 forms of Culex, while the score and more of North American species of 



Fic. 415. — A malaria-carrv-ing mosquito, Anopheles maculipennis; lana at left, in 

 middle two eggs below and pupa above, male adult at right. (From life; much 

 enlarged.) 



Culex compose most of the hordes of piercing and blood-sucking mosqui- 

 toes which in so many localities make life distressful. Slegomyiu jasciuta is 

 found in this country only in the Gulf states. In our colonies, the Hawaiian 

 and American Samoan Islands, I have found it to be the most abundant mos- 

 quito species, although yellow fever is yet unknown in these islands. But 

 it seems not improbable that, with the cutting of a canal through the Isthmus 

 of Panama so that ships can sail directly from the West Indies to Hawaii 

 continuously within the tropics, Stegomyia individuals infested with yellow- 

 fever germs might be readily carried to our tropical Pacific colonies. Such 

 a possible contingency should at least be had in mind by those charged with 

 the responsibility of public-health affairs in Hawaii and Samoa. Slegcmyia 

 is already terrible enough in its disease-spreading capacity in unfortunate 

 Samoa, as explained in Chapter WHI, the frightful scourge elephantiasis, 



