The thorax consists of three segments viz., pro, meso and metathorax and each bear onepair of legs called fore, middle and hind legs respectively. Legs are the principal organ oflocomotion and they have undergone many modifications and have been adapted to wide rangeof functions. The generalized insect leg consists of six segments.
1. A basal COXA (articulating with the thorax in the pleural region)
2. A small TROCHANTER
3. A FEMUR (largest part)
4. A TIBIA
5. 1-5 Segmented TARSUS (Pl. Tarsi)
6. A PRETARSUS (insect foot) and two claws and a pad called arolium
Modification of Insect Legs
1.Ambulatorial.
Walking, segments more or less uniform
Ex – Fore legs and middle legs of grasshopper
2.Cursorial
Walking and running, segments generally long and slender
Ex-Cockroaches
3.Raptorial
Grasping, femur and tibia enlarged with row of spine
Ex – Forelegs of preying mantis
4.Fossorial
Digging, forelegs bearing heavily sclerotized claws adapted for digging soil tarsi digitated
Ex – Fore leg of mole cricket
5.Scansorial
Clinging, tarsus is one segmented with a single strong, sickle shaped claw
Ex – Forelegs of head louse
6.Natatorial
Swimming, oarlike, tibia and tarsus much flattened and fringed with dense hairs.
Ex – Hind leg of water scavenger beetle
7.Saltatorial
Jumping, Femur of the hindlegs are enlarged and accommodating the muscles used for jumping
Ex.-Hind legs of Grasshopper
8.Clasping legs
Clasping, Tarsus is one segmented and arched, during reproduction this adaptation enables the male to hold the female
Ex-Foreleg of male water diving beetle
9.Prolegs/ pseudo
legs
Ex-Abdominal legs of lepidopteran larva
10.Foragial
Pollen gathering, Coxa, trochanter and femur are normal in shape, while the tibia of hind leg is dilated and covered with long dense hairs thus forming a pollen basket or corbicula and meant for storing the pollen grains.
Ex-Hind legs of worker honey bee
