Spiracles are openings in the exoskeleton that allow air to enter the insect. Which of the following best describes spiracles?

• A. Gills located near the abdomen for oxygen exchange.
• B. Openings in the exoskeleton that allow air to enter the insect.
• C. Tiny air sacs in the thorax that store oxygen.
• D. Specialized hairs that sense air currents.

Answer: (B)

Spiracles are the external openings that begin the insect’s respiratory system. They connect the outside air to a branching network of tubes called the tracheae and tracheoles, which deliver oxygen directly to every cell. Gas exchange happens mainly in the tiny tracheoles that extend to tissues, so spiracles serve as the entry points for air to reach this system. They can open to let in oxygen and close to reduce water loss in dry conditions.

This isn’t about gills, which are adapted for extracting oxygen from water in aquatic animals. It also isn’t tiny air sacs in the thorax that store oxygen—spiracles are openings, not storage structures. And it isn’t specialized hairs that sense air currents—they’re sensory structures, not pathways for air entry into the body.