How did DDT become ineffective against mosquitoes ?

Explanation

**Step-by-Step Solution:**

1. **Introduction to DDT**: DDT (Dichloro-Diphenyl-Trichloroethane) is a synthetic insecticide that was widely used to control mosquito populations and other pests in agriculture and public health.

2. **Initial Effectiveness**: Initially, DDT was very effective in killing mosquitoes and reducing their populations, which helped in controlling diseases like malaria.

3. **Development of Resistance**: Over time, mosquitoes began to develop resistance to DDT. This resistance did not occur overnight but was a gradual process.

...