Like many other insects, cockroaches lack lungs. Instead, their respiratory system is made up of a network of tubes called tracheae, which open to the outside through paired, valve-like structures known as spiracles located on the thorax and abdomen. Muscles around the spiracles keep them mostly closed but allow them to open when the insect needs to draw in oxygen-rich air or expel carbon dioxide. The tracheae, which connect to the outer body cuticle, branch into smaller tubes called tracheoles. Through the thin walls of the tracheoles, oxygen and carbon dioxide diffuse directly into and out of the tissues.
In less active insects, gas exchange primarily occurs through passive diffusion across the body surface. Cockroaches, however, are highly active, and like other energetic insects such as dragonflies, ants, and bees, they rely on mechanically ventilated respiratory systems.
Rhythmic movements of the abdomen pump air in and out, forcing oxygen into some spiracles while expelling carbon dioxide from others. These movements change pressure within the tracheae, causing sections of the tubes to inflate and collapse, which helps circulate air through the network. The system can also respond to heat stress or low oxygen and high carbon dioxide levels, triggering nerve centers that increase the rate of respiration.
