One quarter of all the known species on Earth are beetles.

Body Systems

Bug bodies are very different to our bodies. Bugs eat, excrete, breathe, and sense their world as we do, but in very different ways.


Bugs have their skeletons on the outside of their bodies. The hard, segmented cover is called an exoskeleton. Made of chitin, it is strong but also light and flexible. The exoskeleton provides support and protection, and has evolved into many shapes, textures and colours. It is covered in a thin layer of wax, which waterproofs the animal and stops it losing water from its body. The segments are joined together by soft tissue to allow movement.


You have a mouth that delivers chewed food to your stomach and intestines. Bugs have a long and tube-like digestive tract, often made up of three sections, each with different functions. Food travels from the mouthparts down the digestive tract, with most of the ‘chewing’ done in the first section or ‘foregut’.


You have a ‘closed blood’ system. Your heart pumps blood through arteries and veins around your body. Bugs have an ‘open blood’ system in which a single tube with a series of pumps—or hearts—moves blood in one direction along its length. Blood ‘washes’ over the organs and returns along the tube.


Your blood is cleaned of wastes as it is pumped through your kidneys. Bugs have malpighian tubules that float around inside the body cavity, extracting waste products from the blood that washes over them.


You have a nose that leads to two large air sacs—your lungs. Insects and most spiders breathe through a series of openings, called spiracles, which are situated along their bodies. The air travels down tubes, delivering oxygen to all parts of the insect’s body. The spiracles can also be sealed, allowing the insect to stay dry, or to prevent moisture loss in hot conditions. Most spiders also breathe through spiracles. A few spiders have simple lungs called ‘book lungs’.

Nervous System

You have a brain that is connected to your spinal cord along your back. Your brain controls the activities throughout your body. Bugs have a nerve cord on their underside with ‘mini-brains’, or ganglia, along its length. These mini-brains can work independently. If an insect loses its head, it does not die immediately but eventually starves to death because it can’t eat.

 Beetles  Katydids
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Giant Burrowing Cockroach, link to large image Giant Burrowing Cockroach

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Spotted Predatory Katydid, link to large image Spotted Predatory Katydid

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Diving Bettle, link to large image Diving Beetle
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