Journal of Mosquito Research 2015, Vol.5, No.13, 1-5
4
might also be a serious pest in certain situations.
Simultaneous attacks by both the species of mosquitoes
on the same bait both at indoor and outdoor locations
were observed. The environment of the Marble palace
was found to be more favourable for the population
build up of
Ae. albopictus
than for
Ae. aegypti
during
the present study. A comparison with the previous study
conducted on larval population (Gilotra et al., 1967) in
the same niche suggested a possible competitive
displacement between populations of
Ae. aegypti
and
Ae. albopictus
and this displacement during the
present piece of work was in favour of
Ae.
albopictus
mosquitoes.
This garden, where
Ae. albopictus
activity had been
continuing for a prolonged period, might act as an
epicenter to spread its population in the city of Kolkata.
Further in depth study is required related to the
population densities of
Ae. aegypti
and
Ae. albopictus
in the whole city of Kolkata as there are evidences of
the spread of population of
Ae. albopictus
in Singapore
Reunion Island, Japan etc.(Yoshikawa et al., 2004) for
beautification of cities and also for uplift of environment,
which are suitable for the breeding of
Ae. albopictus
.
2 Materials and Methods
The study period extended from September 1986 to
August 1987 in the marble palace garden of central
Calcutta. The study was permitted by the ethical
committee, Calcutta School of Tropical Medicine. For
man-landing captures of mosquitoes the method
adopted by Hati and coworkers (Hati et al., 1981) was
followed. Hati et al., (1981) conducted man-bait
collections during night for 12 hours but during the
present study collections were conducted throughout
the day and night i.e. for 24 hours.
Description of the Study Area
The area of the garden was 40,000 m
2
situated in a
thickly populated area in Central Kolkata, with
various plants, shrubs, bushes, herbs, a two storied
marble building, several brick-built houses, a mini zoo
(having few deer, peacock, cranes, cuckoos, a variety
of small birds, rabbits, tortoise and monkeys) a car
garage containing a pile of old tyres, a cattle shed and
a horse stable. The animals were provided with
drinking water in large molluscan shells and earthen,
aluminium and tin pots.
The collection of mosquitoes off human baits
(volunteers) was performed twice in a month. The
indoor bait was placed in a room (10m
×
5m
×
8m) of
the garden with two windows and one door. In open
air, about 10 m away from the indoor bait, outdoor
captures were made off the out door bait. At both
indoor and outdoor, one man in each case was lying
on a wooden cot, 0.5m above the ground wearing only
shorts to serve as baits. Such human baits of the same
age group were kept for 24 hours (6 a.m. to 6 a.m. of
the next day) both at indoor and outdoor. In winter
months, when the upper and lower extremities and
belly were exposed, the chest and waist were wrapped
in blankets. During rain the outdoor bait was protected
by plastic sheets 4 m
×
3 m placed 3 m above the bait
supported by 4 bamboo poles. Mosquito collectors
were fully dressed with full sleeve white aprons, white
trousers and cotton made shoes. The head of each
collector was also covered with a white cap. For each
of indoor and outdoor bait three collectors were
allotted. The man-landing mosquitoes were caught
with the help of battery operated torches and test tubes
from 6 a.m. to 6 a.m. of the next day. Two of the
collectors collected mosquitoes from two sides of the
human bait and the third man noted the time of
collection and the body parts from which the mosquitoes
were collected. Hour wise catches of man-landing
mosquitoes were kept in test tubes, plugged with
cotton separately and identified in the central laboratory.
Volunteers and mosquito collectors were replaced as
and when required from the reserve. Hour wise,
quadrant wise (a 12 hour day light period was divided
in 4 quadrants of 3 hours each) and month wise numbers
of caught man-landing mosquitoes were noted.
Acknowledgements
We are grateful to ICMR for providing financial assistances.
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