116 
c. Epidemiological. Williams (1937a) 
stated, “Punctipennis, although capable of 
transmitting the disease and occurring in 
considerable quantities in all parts of the 
United States is wholly an outdoor biter 
and enters houses only in the late fall 
and then apparently for the purpose of 
hibernation. ’ ’ 
The available data indicate that A. punc¬ 
tipennis is susceptible to infection with the 
three main species of plasmodia, but that 
it is a less effective vector than A. quadri- 
maculatus. Further studies will be re¬ 
quired to determine more exactly its rela¬ 
tive importance in the different regions 
where it exists. 
5. Anopheles (Anopheles) Quadri- 
maculatus Say 1824 
a. Experimental infection. The suscep¬ 
tibility of A. quadrimaculatus to experi¬ 
mental infection with the three main species 
of malaria plasmodia has been well estab¬ 
lished and because of the ease with which 
this mosquito can be reared in captivity it 
has been used extensively for the routine 
transmission of malaria in the treatment of 
paresis. This use has afforded an unusual 
opportunity to study its characteristics as 
a vector in great detail and thanks to the 
extensive experiments of Boyd and his 
associates and of others, a fund of valuable 
fundamental information is now available 
concerning the development of the different 
plasmodia in A. quadrimaculatus under 
various conditions. Since the literature on 
this subject is too extensive to be reviewed 
here, the reader is referred to the original 
publications for complete details. The data 
given below are limited to information 
summarized by Covell (1927; 1931b) and 
other earlier investigators and to a few of 
the more recent observations made by Boyd 
and his co-workers. 
P. vivax. In 1900 Thayer reported the 
experimental infection of A. quadrimacu¬ 
latus with P. vivax and this observation 
was soon confirmed by Berkeley (1901), 
King (1916a, b) Mitzmain (1916b) and 
others. More recently Boyd and his asso¬ 
ciates have shown that A. quadrimaculatus 
is an effective experimental vector of P. 
vivax. The minimal parasite density re¬ 
quired to infect A. quadrimaculatus is 
about one male and one female game- 
tocyte per 100 leukocytes (Boyd, Strat- 
man-Thomas and Kitchen 1935), and the 
intrinsic incubation period at 20° C is 
about 17 days (Boyd 1934). In a study 
of the influence of temperature on the 
sporogenous cycle of P. vivax, Stratman- 
Thomas (1940) found that the cycle was 
completed within the temperature range of 
15-17° to 30° C; the shortest time after the 
infective feeding was 8 days and the longest 
38 days. The optimum temperature was 
28° C. Shortly after feeding on a game- 
toeyte carrier, A. quadrimaculatus was 
rendered non-infective by 2 to 3 hours’ 
exposure to 37.5° C, 24 days’ exposure to 
1°-10° C. Seven to 13 days after feeding 
the development of oocysts was aborted 
by exposure to 37.5° C for 18 to 24 hours, 
or to 1°-10° C for 24 days. After com¬ 
pletion of the sporogenous cycle the in- 
fectivity of the sporozoites in the salivary 
glands was markedly inhibited by exposure 
to 37.5° C for 24 hours or to l°-7° C for 
50 days. The author remarked that “The 
fact that P. vivax will not develop at a 
constant temperature above 30° C, and the 
fact that a period of 24 hours at 37.5° C 
will sterilize all but a very small per cent 
of A. quadrimaculatus of their P. vivax 
infection, have a bearing on the transmis¬ 
sion of P. vivax infection during the sum¬ 
mer months. The data presented show that 
in certain localities the oocyst may survive 
the winter and complete its development 
the following spring.” A study of the 
per cent of A. quadrimaculatus infected 
experimentally with P. vivax in 230 batches 
(Boyd and Kitchen 1938b) showed that a 
higher proportion of mosquitoes were in¬ 
fected in the batches applied during the 
spring and autumn. 
Boyd, Kitchen and Kupper (1937) re¬ 
ported that of 3,574 A. quadrimaculatus 
fed on P. vivax gametocytes, 2,288, or 64.2 
per cent, were infected. Boyd (1937) 
compared the susceptibility to P. vivax of 
a certain strain of A. quadrimaculatus 
