118 
M AT. ART A 
Thomas (1933a) reported the first recorded 
experimental transmission of P. malariae 
by anopheles mosquitoes. In four lots of 
40, 63, 18 and 42, A. quadrimaculatus the 
per cent infected were 45, 32, 63.4 and 
9.4, respectively. The extrinsic incubation 
period at 20° C was 30 to 35 days. In 
1936 these authors reported the transmis¬ 
sion of quartan malaria to two additional 
cases. 
b. Inf ection in nature. Hirshberg (1904) 
reported the finding of “naturally in¬ 
fected” A. quadrimaculatus and since that 
timeMitzmain (1916e, 1919), Metz (1919c), 
King (1921), Root (1924b) and Darling 
(1925) have reported infections in nature 
ranging from 0.3 to 19.0 per cent. 
c. Epidemiological. A. quadrimaculatus 
is universally regarded as the most impor¬ 
tant malarial vector in the United States, 
because of its breeding and feeding habits, 
its susceptibility to infection and its dis¬ 
tribution in malarious regions. According 
to Williams (1937a), it is the chief vector, 
a conclusion that may be accepted for the 
United States. It breeds almost wholly in 
still water that is relatively clear. It re¬ 
quires some sunshine, never being found 
in dense shade. However, it requires some 
darkness, never being found in waters 
which are wholly unshaded, unless they 
have a type of flotage which casts narrow 
strips of shade where the mosquito larvae 
may lie during a portion of the daylight 
hours. Although A. quadrimaculatus will 
feed on animals, as does A. punctipennis, 
it will also feed voraciously on human be¬ 
ings and frequents human habitations. 
6 . Anopheles (Anopheles) walkeri 
Theobald 1901 
a. Experimental infection. — P. vivax. In 
August 1932 Matheson, Boyd and Strat- 
man-Thomas (1933) reported experiments 
performed in Florida with 8 imagines of 
A. walkeri from larvae collected in New 
York. Six of them fed on a tertian patient 
whose blood had a gametocyte density of 
16 males and 3 females per 100 leukocytes 
and exflagellation of the males. The next 
day one other mosquito fed. The mosqui¬ 
toes were kept at a temperature of 19 °- 
22.8° C. Six specimens were examined and 
4 were infected, the extrinsic incubation 
period being estimated at about 17 days. 
One specimen transmitted the infection to 
a human patient. 
P. falciparum. During 1926 Komp in 
Louisiana attempted to infect A. walkeri 
with P. falciparum with negative results. 
In October 1935 Kitchen and Bradley 
(1936a) applied groups of A. walkeri, col¬ 
lected in Florida, and control groups of 
A. quadrimaculatus to a patient with P. 
falciparum malaria. On the days of these 
feedings the gametocyte densities were: 
male, 540 to 580; female, 250 to 340 per 
cmm. All dissections were made 12 days 
later with the following results: A. quadri¬ 
maculatus, total fed 26, positive 20, or 77 
per cent; A. walkeri total fed 9, positive 
1 (1 cyst), or 11.1 per cent. It was con¬ 
cluded that the southern form of A. walkeri 
is not highly susceptible to infection by 
P. falciparum. There are no data for P. 
malariae. 
b. Infection in nature. From July 11 to 
29, 1939, Bang et al. (1940), using a light 
trap, collected mosquitoes from the environs 
of Bondurant, Kentucky. The 231st speci¬ 
men of A. walkeri dissected had oocysts 
on the stomach and a heavy sporozoite in¬ 
fection of the salivary glands. The authors 
remarked that the human origin of the 
parasites was probably indicated by the 
fact that A. walkeri prefers to feed on 
mammals, including man, rather than birds. 
c. Epidemiological. Johnson (1936) re¬ 
marked that “Possibly due to its willing¬ 
ness to bite humans, its unusual daytime 
resting habits, and its presumably unrecog¬ 
nized prevalence, A. walkeri may be shown 
to be of importance from the malaria stand¬ 
point. This of course is dependent on its be¬ 
ing an efficient harborer of the malaria or¬ 
ganism.” According to Williams (1937a), 
“The place of A. walkeri as a malarial 
vector is in some doubt. Until two years 
ago it was considered a very rare mosquito. 
It was found breeding in only a few places 
in the grassy edges of swamps. So few 
specimens were encountered that it was 
