Structure and modifications of insect legs.

Structure of insect legs

The fore-legs are located on the prothorax, the mid-legs on the mesothorax, and the hind legs on the metathorax. Each leg has six major components, listed here from proximal to distal: coxa (plural coxae), trochanter, femur (plural femora), tibia (plural tibiae), tarsus (plural tarsi), pretarsus. The femur and tibia may be modified with spines. The tarsus appears to be divided into one to five 'pseudosegments' called tarsomeres. The term pretarsus refers to the terminal segment of the tarsus and any other structures attached to it, including:
> ungues -- a pair of claws
> arolium -- a lobe or adhesive pad between the claws
> empodium -- a large bristle (or lobe) between the claws
> pulvilli -- a pair of adhesive pads

Like the mouthparts and antennae, insect legs are highly modified for different functions, depending on the environment and lifestyle of an insect.

LEG MODIFICATIONS

> Saltatorial -- jumping

> Raptorial -- seizing

> Fossorial -- digging

> Natatorial -- swimming

> Cursorial – running

> Ambulatory- walking

> Ambulatory legs

1. Ambulatory legs:

Ambulatory legs are used for walking. The structure is similar to cursorial (running) legs. Examples: Bugs (order Hemiptera), leaf beetles beetles (Corder oleoptera).

2. Saltatorial legs

Saltatorial hind legs adapted for jumping. These legs are characterized by an elongated femur and tibia. Examples: Grasshoppers, crickets and katydids (order Orthoptera).

3. Raptorial legs

Raptorial fore legs modified for grasping (catching prey). Examples: Mantids (order Mantodea), ambush bugs, giant water bugs and water scorpions (order Hemiptera).

4. Fossorial legs

Fossorial fore legs are modified for digging. Examples: Ground dwelling insects; mole crickets (order Orthoptera) and cicada nymphs (order Hemiptera).

5. Natatorial legs

Natorial legs are modified for swimming. These legs have long setae on the tarsi. Examples: Aquatic beetes (order Coleoptera) and bugs (order Hemiptera).

6. Cursorial legs

Cursorial legs are modified for running. Note the long, thin leg segments. Examples: Cockroaches (order Blattaria), ground and tiger beetles (order Coleoptera).