194 Arthropods as Hosts of Pathogenic Protozoa 
'proof hut. Though they took no quinine'and all of their neighbors 
suffered from malaria, they were absolutely free from the disease. 
To complete the proof, mosquitoes which had fed in Rome on 
malarious patients were sent to England and allowed to bite two 
volunteers, one of them Dr. Manson’s own son, who had not been 
otherwise exposed to the disease. Both of these gentlemen con¬ 
tracted typical cases of malaria and the parasites were to be found in 
abundance in their blood. 
Since that time there have been many practical demonstrations 
of the fact that malaria is transmitted exclusively by the bite of 
mosquitoes and that the destruc¬ 
tion of the mosquitoes means the 
elimination of the disease. 
We have said that the malarial 
parasite is able to undergo its 
development only in certain 
species of mosquitoes belonging 
to the Anopheline group. It is 
by no means certain that all of 
this group even, are capable of 
acting as the definitive host of 
the parasites, and much careful 
experiment work is still needed 
along this line. In the United 
States, several species have been 
found to be implicated, Anopheles 
quadrimaculatus and Anopheles 
crucians being the most common. The characteristics of these species 
and the distinctions between them and other mosquitoes will be 
discussed in Chapter XII. 
In antimalarial work it is desirable to distinguish the anopheline 
mosquitoes from the culicine species in all stages. The following 
tabulation presents the more striking distinctions between the groups 
as represented in the United States. 
Anopheles Culex, Aedes, etc. 
Eggs: Laid singly in small Deposited in clumps in the 
numbers upon the surface of the form of a raft (Culex group) or 
water. Eggs lie upon their sides deposited singly in the water or 
and float by means of lateral on the ground in places which 
expansions (fig. 127). may later be submerged. 
127. Eggs of Anopheles. After Howard. 
