Bacillus thuringiensis israelensis (Bti) is described as the most widely used bacterial protein that kills instars 1-4. Which statement is accurate?

• A. Bti kills only adult mosquitoes.
• B. Bti kills larval instars 1-4.
• C. Bti kills eggs.
• D. Bti has no effect on mosquitoes.

Answer: (B)

Bti acts as a biological larvicide that targets mosquito larvae. The crystal toxins it produces are activated in the larval gut after ingestion, damaging midgut cells and killing the larvae before they become pupae or adults. This makes it effective specifically against aquatic larval stages, particularly instars 1–4, while eggs and adult mosquitoes are not affected. That’s why the accurate statement is that Bti kills larval instars 1-4. It’s widely used because of its safety for non-target organisms and humans and its ability to interrupt the life cycle before adults emerge.