If breathing is defined as the rhythmic movement of air into and out of the lungs, then insects don’t technically breathe as they lack the necessary organ.
Instead, air passively enters their bodies through a series of spiracles (holes) in their thorax and abdomen. It then passes into a network of tubes called tracheae that branch off into tissues where gas exchange takes place. Without blood to carry it around the body, oxygen is delivered directly to the insect’s tissues, and carbon dioxide is expelled.
This efficient system allowed insects to grow to giant proportions in the distant past, when atmospheric oxygen concentrations were higher. The largest known example in the fossil record is Meganeura, an ancient relative of today’s dragonfly, with a wingspan of 71cm.
In everything from dragonflies to beetles, muscles are used to control the spiracles like valves, relaxing to open and contracting to close. Larger species of insect, such as locusts, have also been observed ‘abdominal pumping’, which could be compared to inhaling and exhaling.
By flexing their abdomens, they force air in and out of their body. This increased respiration boosts oxygen levels to help the creatures deal with heat, stress or the exertion of flight.
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