Of the countless anatomical mysteries in the animal kingdom, many involve insects. For example, without lungs or a diaphragm to help them inhale and exhale, how do ants and other insects breathe?
Insects have openings along their exoskeletons called spiracles that take in air. For ants and other small insects up to about two centimeters in length, the air then diffuses along a network of tubes called tracheae, which narrow as they spread through the insect’s body. Unlike mammals, which rely on our blood to carry oxygen to our cells, the simple process of diffusion eventually brings air to a branch of the tracheae that touches the membrane of a cell, providing oxygen directly. Carbon dioxide, the waste product of cellular respiration, diffuses out in a similar process.
Larger insects also rely on spiracles and tracheae, but random diffusion of air molecules will not provide their cells with oxygen quickly enough. Instead, their breathing process is much more active, involving flexing the abdomen to get air moving along the tracheae. However, as they still rely on diffusion rather than active respiration like mammals, the maximum size to which insects can grow is limited (you won’t find many larger than the Goliath beetle, which can measure up to 4.3 inches and weigh up to 100 grams).
Breathe in, breathe out:
- Though they may be just 0.1 millimeters in diameter, the spiracles of tiny insects provide all the oxygen their bodies need to survive. In fact, the spiracles work so well that they are sometimes closed to avoid overloading the creature with oxygen.
- An insect’s spiracles may also close to help conserve water. This is particularly important in hot and humid climates, as it prevents them from becoming dehydrated.
- Due to their ability to close spiracles to take part in discontinuous gas exchange, many insects can recycle the oxygen in the tracheae, eliminating the necessity for constant respiration. This allows insects to survive for days without breathable oxygen, including in hypoxic soil or underwater.
