v Mosquitoes as Disease-Carriers. 87 
and yet the closely related human parasites cannot; possibly they 
may in other genera such as Jaiifhinosoma, Mucidus, etc.* 
When we examine the distribution of the Anopheles we find 
that it tallies very well with the chief centres of malaria. 
Anopheles are associated with swampy districts and marshes, and 
it is in these districts that malaria chiefly occurs; but they are 
often found in villages and houses, breeding in pools and so forth, 
close to them. The only district where malaria occurs, from 
whence collections have been received which contained no 
Anopheles , is Victoria. The specimens sent from the malarious 
district of the uplands of Victoria were Steyomyia fasciata, 
or, as it has been called in Australia, Gulex Bancroftii, 
Skuse. Although no Anopheles have been sent from Mauritius, 
I find three species are found there; one is abundant in the 
parts of the island where malaria is most prevalent.! From 
parts of South America but few Anopheles have been received ; 
but from such fever-stricken districts as the West Coast of 
Africa, the Malay Peninsula, and the West Indies, Anopheles 
have been sent in numbers; also from the north of South 
America (British Guiana, &c.). In fact, the whole distribution 
of the genus fits in well with the distribution of malaria. This 
subject has been more fully worked out for England by Dr. Nuttall, 
who tells me the distribution map of our three Ampheles corre¬ 
sponds with the old malarial district map he has prepared. 
It is not in the province of this work to enter fully into this 
subject; but I may point out that considerable evidence has been 
collected showing how readily Anopheles breed in the small 
pools and puddles that collect after heavy rain on newly broken 
soil. Malarious outbreaks have often accompanied the breaking- 
up of soil and the formation of railroads, and can thus easily be 
accounted for by the opportunities given the Anopheles to breed 
in larger numbers than usual. An enormous percentage of the 
native population seems to contain the malarial parasites in their 
blood, although the disease does not affect them, so that the 
intermediary host has always plenty of opportunity to become 
infected, and so distribute the disease to healthy people. 
Mr. Budgett writes me that he partly attributes his 
immunity from fever, during his recent Gambia visit, to living 
some way from native quarters and to other safeguards he 
* Dr. Daniels has experimented with Pcmoplites and found the African 
species takes no part in malaria-carrying. 
f Annual Report, Museum, Colony of Mauritius, 1898-99, p. 4. 
