Many insecticides work on the insect's ________ system.

• A. Digestive
• B. Nervous
• C. Circulatory
• D. Excretory

Answer: (B)

Insects rely on their nervous system to coordinate movement, feeding, and responses to danger, so many insecticides are designed to disrupt nerve signals. When a neurotoxic insecticide interferes with nerve transmission, the insect can’t move properly or respond to stimuli, leading to paralysis and death. A common way this is achieved is by inhibiting the enzyme acetylcholinesterase, which normally breaks down the neurotransmitter acetylcholine. If acetylcholine accumulates, nerves fire uncontrollably, quickly exhausting the insect and causing irreversible paralysis. There are other insecticides that act as stomach poisons and affect digestion after ingestion, but these tend to be slower and less consistently lethal than those that target the nervous system. This rapid disruption of neural communication is why the nervous system is the primary target for many insecticides.