The largest and most successful groups of insects are the beetles. All beetles have two pairs of wings, but only the back pairs are used for flying. The front wings, called the elytra, form a hard, protective case. This fold over the fragile back wings when the beetle is on the ground. As the beetle takes off, the elytra open. Some beetles do not fly at all, so their elytra are fused together.
The hard elytra are good protection against predators. Many beetles also have other methods of defence, such as squirting poisonous chemicals at their attackers, or startling them with loud noises.
Beetles hatch from their eggs as grub-like larvae. They grow and then pupate, emerging as fully-grown adults. Some plant-eating beetle larvae are legless grubs, while predatory beetle larvae have large jaws and legs which they use to catch their prey.
Fleas live on or near the bodies of animals, feeding on their blood and so often spreading diseases from one animal to another. Fleas carried on the bodies of rats were responsible for the plague in the 14th century, known as the Black Death. Fleas have a powerful “trigger” in their hind legs that allows them to travel over 100 times their own length in a single leap.
Some flies also feed on blood, biting animals and humans and spreading disease. However, most flies are very useful insects. Many help to pollinate flowers by feeding on nectar and pollen, while others are scavengers. They actually help to keep our environment clean and healthy, by feeding on dung or rotting material such as dead plants and animals.
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