Question

Spraying kerosene on stagnant water shall kill Anopheles due to
A) Prevention of spiracle to come in contact with air
B) Entry into and blocking of respiratory tract
C) Diffusion into body
D) Burning of body wall

Answer 1

Hint:Malaria which is one of the most common diseases of mankind spreads by the bite of female Anopheles mosquitoes. It is caused by the protozoan Plasmodium that requires two hosts two complete its life cycle- man and Anopheles mosquitoes.

Complete answer:
Mosquitoes are cosmopolitan in distribution, they are nocturnal. The remarkable fact about them is that their females are adapted for sucking human blood and some genera of mosquitoes are the vectors for various diseases like malaria, dengue, filariasis, etc.
Mosquitoes breed and develop in stagnant water so if such water is removed, it will prevent the breeding of mosquitoes.
The destruction of pupae and larvae of mosquitoes can be achieved chemically and biologically. The spraying of some oils such as kerosene oil, petroleum, paraffin oil, crude oil, etc. on the surface does not allow larvae to breathe and consequently, they die due to suffocation.
Cultivation of larvivorous fishes like Gambusia is another important control measure for mosquitoes. These fishes eat their larvae and pupae.
Application of mustard oil or citronella oil or some repellent cream on uncovered body parts of the body keeps mosquitoes away.

So the correct answer is -B. The oil kills Anopheles mosquitoes due to entry into and blocking of the respiratory tract.


Note:Mosquitoes are associated with the transmission of a number of diseases that may sometimes prove fatal so it is important to control them by eradicating their breeding places.