KING INSTITUTE, GUINDY, FOR 1927-28
13
3.90 per cent for the other two species. This confirms the conjecture of the last
report that most probably culicifacies was the chief carrier. This is more clearly
shown by taking the totals of the infected females. Thus 23 infected culicifacies
were found as against nine stephensi and three listoni. The mosquito infections
were as follows :—
A. culicifaci's.
A. stephensi.
A. listoni.
Zygotes found in
...
...
18
9
3
Sporozoites found in ...
...
4
1
0
Village differences.—Considering differences in mosquito population, it is very
evident that villages of group A in the irrigated Mopad area have more infected
adults than any other group. The mosquito infection rates of this group and of
the next group B are practically the same, but mosquitoes being so much more
numerous in A than in B suggests that conditions for breeding or maintaining
adult anophelines were more favourable in A than in B. The diminution in the
number of mosquitoes and absence of infected mosquitoes in groups C and D is
to be noted. Further the absence of malaria-carrying anophelines from two
villages, Nutssupoda and Tsallavaripalli in C and D that had the least malaria
according to Table X is very striking. We may say that on the whole Table XII
confirms Tables X and II in showing how much more favourable for malaria are
the mosquito conditions in the villages where malaria is shown to be worse.
5. Breeding places of malaria-carrying anophelines—(See Map 111) Com-
parison with previous visit .—Despite the more favourable season, breeding
places were practically the same in extent and amount of breeding as those
already described in the first report, which is to be accounted for by the failure
of the rains. The sub-soil water level throughout the tract in November not
only was not higher, but in places such as Mopad Village was even lower than
in March. The level of the Mopad Reservoir was lower at the second visit than
at the first, The fact that adult mosquitoes were found in abundance at the
second visit despite the failure of the monsoon in the production of rains and so
despite any appreciable increase in breeding facilities, tends to confirm the
suggestion made in the first report that monsoon seasons favour malaria in locali-
ties such as the Mopad tract where breeding facilities abound, chiefly by the fact
that their accompanying atmospheric conditions of temperature and humidity
promote a longer life in anophelines and assist the development of the malaria
parasites in the mosquito.
Differences in species found.—In almost all cases the three species incriminated
were found together in the same breeding place, so that there is no need to
mention minor differences in breeding places when one or other of the three
species was missing. A fuliginosus was found breeding in pools at the edge of
the Mopad reservoir towards Inimerla and nowhere else. Adults of these species
were not found.
Variety of breeding places.— The low lying parts of the Mopad irrigated area
appears to be water-logged, see photos for there are innumerable collections of
water in pits and drainage channels which breed anophelines—see first report.
Further there appears to be very little attempt to drain the land ; such drains as
exist appear to have been self-formed for they are irregular and in parts spread
out making good breeding places. Breeding conditions are greatly facilitated by
the shelter given to larvae by the presence of Jumbo grass which grows freely
throughout the area in all collections of water. This is a tall grass growing up
to five or six feet out of stagnant or slowly running water. The assistance this
affords to breeding is well seen in minor canals for where these are free from the
grass larvæ are not found, but whereas—in many places they are almost choked
with the grass there larvæ abound. Here we may note that Jumbo grass is not
found in the irrigated area south of the aqueduct which is an indication of the
better conditions that prevail there as regards less stagnation of water.
Next in importance to the many breeding places throughout the Mopad area
is the bed of the Maneru river in the section bounding the area on the north.
This is practically a series of pools full of jumbo grass and anophelines—see
photos 6 and 7.