bio

Spiracle

The small valved pores along an insect's body where air enters the tracheal system - tiny pipes that carry air straight to the tissues, bypassing blood entirely. Wonderfully efficient at small size, but with a hard ceiling: passive diffusion down a tube fades fast with distance, so the pipes cannot reach the core of a large body. The only era that ever grew giant insects - dragonflies with a hawk's wingspan - was a stretch of deep time when the air held far more oxygen, enough to force its way deeper down those pipes.