Discuss some effective methods in controlling the houseflies and cockroaches.

Following measures can be taken to stop the spread of houseflies and cockroaches:

1. Killing mosquitoes by spraying DDT or other insecticides.
2. Eliminating mosquito breeding sites, especially in stagnant water
3. Destroying larvae and pupae of mosquitoes by spraying kerosene or greasy oil over stagnant water bodies.
4. Introducing fishes such as Gambusia can reduce mosquito larvae.
5. Storing garbage in tight lid bins.
6. Proper disposal of water
7. Keeping food covered.