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KMID : 0353019660030010023
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Korean Journal of Public Health
1966 Volume.3 No. 1 p.23 ~ p.31
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Experimental Study on the Control Measures of Medical Insects
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Abstract
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The responses and behaviour of A. sinensis to DDT residual spraying were studied by means of esperimental huts fitted with window traps.
The two huts were of the local style, inner size are 3.1m x 2.2m with the wall 1.85m high, built of mud blocks,thatch roofs and prepared ceilings. The entrance was attached a screened door. Four window traps 40.5cm square size and four panels with entrance cone were attached to each of four walls. One of the huts was left unsprayed for control, the other one was sprayed with DDT at 2gm/m².
Method of mosquito collection
Before the each catching, resting mosquitoes in the huts were thoroughly searched instead of pyrethrin spraying to clean. At dusk, the window traps were fixed and a big white sheet spread on the floor, stretched to the wall. A cow entered each hut at 08:00p.m. At sunshine the the floor sheet folded up, taken out and dead mosquitos were collected. Then the traps, its opening closed, were romoved. The dead mosquitoes in the traps were taken out and the living specimens transferred in to paper cups with mosquito netting and provided with sugar solution; they kept in the field laboratory for further observations.
Observations
1. The number of A. sinensis collected from the DDT sprayed hut by means of entrance traps significantly decreased in the first five days after the spraying. DDT in the sprayed hut immediately showed signs of intense irritation or repellency and gradually decreased in the second five days; no repellent effect was noted in the third five days after spraying.
The results revealed that the spraying with DDT does not prevent the A. sinensis from entering.
2. In the house hounting habit of A. sinensis, a high proportion of mosquitoes which entered both the DDT sprayed hut and the unsprayed hut left the hut in the same night. The percentage of mosquitoes left the huts was 55% and 69% respectively. The little difference of the percentage of the exit mosquitos between two huts indicated that the irritation effect of DDT on A. sinensis was not obvious.
3. The percentage of unfed A. sinensis in the sprayed hut and in the unsprayed hut was 2.6% and 2.4% respectively; no inhibiting effect of DDT on the ability of hungry females to feed in the sprayed hut.
4. There was not much difference in the number of mosquitoes existing the sprayed hut and the unsprayed hut at difference hours of the night.
5. The survival rate after 24 hours of A. sinensis which entered the sprayed hut and the unsprayed hut was 35% and 98% respectively. However, about 60% of A. sinensis collected from the exit window traps attached to the sprayed hot still survived after 24 hours.
6. No significant reduction of density of A.sinensis noticed in the sprayed area: nevertheless, the density was 30-40% lower than in the unsprayed.
7. The proportion of gravid females which collected from outdoor resting places was not much different in the sprayed area and in the unsprayed and the number of unfed females was few in both area.
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