MALARIA SURVEY—METHODS AND PROCEDURES 
297 
If blood specimens are collected from all 
persons in the sample the parasitic index 
may be computed. This is, of course, most 
time-consuming. The presence of parasites 
indicates recent spread of the disease, and 
hence recent infection. 
The persons in the sample subjected to 
splenic examination will necessarily in¬ 
clude, if malaria be present, a varying, 
probably small, proportion of acute clinical 
cases, as well as many latent or chronic 
infections. Those with detectable enlarge¬ 
ment include a few persons in whom blood 
examinations are parasite negative, pos¬ 
sibly representing recovered infections. 
On the other hand, a few whose blood 
examinations are positive will not exhibit 
detectable splenomegaly. The latter, in 
some instances, represent very recent infec¬ 
tions. 
It is most convenient to record the data 
pertaining to each person on a special rec¬ 
ord card with keyed perforations along the 
margins, such as are mow commonly used 
in recording statistical data. The punch¬ 
ing out of these holes for positive data 
simplifies subsequent analyses. The mini¬ 
mal information gathered should include 
the following: date, locality of examina¬ 
tion, name, age, sex, race, residence and 
length of residence in the house and the 
locality, spleen classification, identifying 
number of blood smears, species of para¬ 
site, gametocytes, occupation, malarial 
medication taken, condition of dwelling 
and protection against mosquitoes (diffi¬ 
cult to secure without a domiciliary visit), 
attacks of fever over a period of the last 
year, hemoglobin percentage if desired. 
Four points of great importance are to 
be elucidated by the entomological survey: 
the anophelines of the local fauna, their 
role in the transmission of malaria, the 
water collections wherein they breed and 
the habits of the adults. 
Entomological investigations are usually 
limited to the area to be controlled and a 
bordering area about a mile in depth. 
These investigations require field observa¬ 
tions of the larval and adult insects. The 
ova are also studied at times, but observa¬ 
tions of them are not usually essential to 
the practical ends of a survey. If informa¬ 
tion on seasonal and yearly variations in 
incidence is required, studies are continued 
for a year or more. Exigencies of prac¬ 
tical control work will rarely permit this. 
The location of the residences of infected 
persons on a spot map affords a lead to the 
production areas, at least those of major 
significance, although all water areas 
within average flight range of the district 
in which control is contemplated should 
be studied. If early in the season and 
breeding is just beginning, search for 
larvae alone is most practicable, whereas if 
the season is more advanced, it is better to 
carry on both lines of investigation simul¬ 
taneously. 
The entomologist must become ac¬ 
quainted with the local terrain. Topo¬ 
graphical maps are of assistance in the 
discovery of breeding places. If not avail¬ 
able, these maps should be prepared con¬ 
currently by the engineer. 
As minimal equipment in the search for 
larvae there are required a dipper and 
pipettes, rubber boots and labelled speci¬ 
men bottles. If time permits recurring 
observations, the interval should not be in 
excess of ten days. 
All observations should be entered on 
permanent record cards. The records per¬ 
taining to larvae should afford the follow¬ 
ing minimal data: exact location and date, 
type of water collection and actual level; 
degree of exposure to sun, last significant 
precipitation, aquatic vegetation, number 
of larvae collected by instars, pupae and 
pupal shells collected, local distribution of 
breeding and its ' density, identifications, 
and distance to possible shelters and source 
of blood meal for adults. All breeding 
places discovered should be represented on 
maps by conventional signs and the pre¬ 
sumptive permanency of each area should 
be noted. 
Observations on adults are secured from 
nocturnal catches, the use of traps, and 
captures in diurnal shelters, called capture 
stations. Capture stations may be any 
place where anophelines congregate during 
