Where are the infrared-detecting pit organs located on fire beetles?

• A. In the eyes
• B. On the antennae
• C. On the abdomen
• D. Behind the mesothoracic legs

Answer: (D)

Infrared pit organs are specialized heat-detecting sensors that fire beetles use to locate fires and recently burned trees. Their placement on the thorax, specifically behind the middle legs, keeps the sensory pits close to the body’s core and away from limb movement, while still oriented to sense radiant heat from fires below or ahead as the beetle flies. This thoracic positioning provides a stable, protected mount for delicate heat-receptive tissue and nerves, so the beetle can pick up slight temperature changes in the environment and steer toward suitable sites for breeding. Eyes and antennae are tuned to light and chemical or tactile cues, not to detecting infrared radiation, and placing pits on the abdomen would expose them to more debris and be less optimal for integrating heat signals with flight.