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 newspapers 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 jasciata, 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 
Fig. 415.—A malaria-carrying mosquito, Anopheles maculipennis; larva 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. Stegomyia jasciata 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. Stegomyia 
is already terrible enough in its disease-spreading capacity in unfortunate 
Samoa, as explained in Chapter XVIII, the frightful scourge elephantiasis, 
