What are three reasons larvae are more sensitive to insecticides than adults?

• A. Thicker cuticles, more developed detoxification systems, and lower growth demands.
• B. Thicker cuticles, less developed detoxification systems, and higher growth demands.
• C. Thinner cuticles, more developed detoxification systems, and higher growth demands.
• D. Thinner cuticles, less developed detoxification systems, and higher growth demands.

Answer: (D)

The main idea is that the larval stage is more vulnerable to insecticides because of how their body is built and how they metabolize chemicals during growth. First, larvae have a thinner cuticle, so insecticides penetrate more readily and reach internal targets faster than in adults. Second, they tend to have less developed detoxification systems—fewer or less active enzymes that would normally break down and eliminate toxins—so the insecticide stays active longer inside the body. Third, larvae are in a high-growth, high-feeding phase, which means they ingest more food and experience rapid metabolism; this increases the amount of toxin entering their system relative to their size and makes disruption to development and vital processes more likely to be lethal. If the cuticle were thicker, detox systems more robust, or growth demands lower, larvae would be less sensitive, which is why those traits are associated with reduced susceptibility.