Associate Certified Entomologist (ACE) Practice Exam

How can insecticides enter an insect's body?

1. Only through inhalation

2. Only by ingestion

3. Contact, ingestion, or respiration

4. Only through skin absorption

The correct answer is: Contact, ingestion, or respiration

Insecticides can enter an insect's body through multiple pathways, which include contact, ingestion, and respiration. This versatility is crucial for their effectiveness as pest control agents. Contact refers to the scenario where insecticides are applied directly to the surface of the insect's body, allowing the chemical to penetrate through its exoskeleton. This method is especially relevant for formulations such as sprays or dusts that leave residues on surfaces where insects may come into contact. Ingestion occurs when insects consume the insecticide, often inadvertently, while feeding on plants, bait, or other surfaces treated with the chemical. This pathway is fundamental for insecticides designed for use on crops or in bait formulations, targeting insects at the moment of feeding. Respiration involves the inhalation of volatile insecticide vapors, which can enter the insect's body through its spiracles—small openings that lead to the respiratory system. This route is significant for insecticides that are formulated to act as fumigants or aerosols, allowing them to affect insects that are not directly contacted by liquids or solids. Thus, the correct answer highlights the three primary ways that insecticides can penetrate an insect's body, making it clear that effective pest control can employ multiple mechanisms of action to ensure success.