Insect growth regulators affect which developmental stages?

• A. Only adults
• B. Only immatures
• C. Both adults and immatures
• D. Neither adults nor immatures

Answer: (C)

Insect growth regulators work by interfering with the hormonal controls of growth and development in insects. They either mimic juvenile hormone or disrupt the processes insects use to molt and transition between life stages, such as chitin synthesis needed for shedding a skin during larvae or nymphs.

The reason this best fits the question is that immatures (larvae or nymphs) rely on these hormonal cues to molt and reach the next stage. When IGRs disrupt those signals, development is blocked or abnormal, preventing progression to adults. At the same time, some IGRs can influence adult insects by altering hormonal balances that affect reproduction, egg production, or egg hatch. So, while the main, immediate target is immatures, there can be effects on adults as well, leading to impacts across both developmental stages.