How do contact insecticides enter an insect's system?

Contact insecticides enter an insect's system primarily through the exoskeleton, which is the outer protective layer of insects. When a contact insecticide is applied, it adheres to the surface of the insect's body. Insects do not have skin like mammals, but their exoskeleton can absorb certain chemicals that penetrate the outer layer. Once the insecticide makes contact with the exoskeleton, it can disrupt the insect's physiological processes, leading to effects such as paralysis or death.

The other methods of entry, such as ingestion or inhalation, generally apply to different types of insecticides. Ingestion involves the insect consuming the toxin, often through food or treated substances, while inhalation would pertain to insecticides designed as aerosols or gases that enter the insect's respiratory system. Root absorption typically relates to systemic insecticides that are taken up by plants and affect pests feeding on the plants, rather than direct contact on the insects themselves.