Although all insects have six legs, in some species the legs have specialized functions, and all six legs will not be identical. Certain legs may be designed to help the insect move, grasp, eat, climb, swim, clean itself or defend itself.

All Insects Have Six Legs

All insects have three basic body parts: the head, the thorax and the abdomen. The legs are always attached to the thorax, and there are always three pairs. Insects are a part of a larger group of creatures called arthropods. Creatures with more than six legs, such as spiders and centipedes, also are arthropods but are not insects.

The Structure of Insect Legs

The legs of insects have three long segments--the femur, the tibia and the tarsus--and end in a claw. The segments, however, can be shorter or longer, depending on the needs of each species. In many species such as ants, butterflies and beetles, all three pairs of legs are more or less identical but in some species, the pairs of legs can be quite different to provide special functions.

Getting Around

Some species rely on specialized pairs of hind legs for getting around. Crickets and grasshoppers are familiar examples of insects that have enormous hind legs for jumping to make quick getaways from predators. In contrast, the mole cricket, which burrows underground, does not have large hind legs for jumping but instead has short, wide, paddle-shaped front legs for digging.

Catching Food

Predatory insects sometimes have front legs that are designed for grabbing prey. The praying mantis is a well-known insect whose large front legs can reach out and catch other insects with lightning speed. The front legs have sharp combs for holding onto the captured prey.

Missing and Damaged Legs

You may see insects that do not have six similar legs if one or more of the legs has been damaged. Many long-legged species of insects have legs designed to break off easily if grabbed by a predator, such as a bird. This defense does not harm the insect too much, as the broken leg(s) will usually grow back in time.

Source:

Bug Guide: Insect anatomy

KBS: Insect Defences

More Information:

Bug Guide: Information about insects