Spiracle (arthropods)

A spiracle or stigma is the opening in the exoskeletons of insects, myriapods, velvet worms and many arachnids to allow air to enter the trachea.

In larger insects, spiracle control is more complex and critical for managing gas exchange due to their higher metabolic demands.

Larger insects, such as locusts and some beetles, exhibit active ventilation, where spiracle control works in concert with abdominal movements.

These abdominal contractions force air in and out of the tracheal system, and the spiracles open and close in a synchronized manner to maximize oxygen intake and carbon dioxide expulsion.

Research has shown that neural circuits in the insect's central nervous system adjust the spiracle opening in response to carbon dioxide concentration, ensuring efficient gas exchange and preventing hypoxia or hypercapnia.