This experiment studied the external structure of insect legs and their modifications. It identified the basic parts of the typical insect leg - coxa, trochanter, femur, tibia, tarsus, and pretarsus. Several types of leg modifications were observed: simple walking legs, jumping legs, digging legs, pollen carrying legs, grasping legs, swimming legs, and legs modified for upside down walking. Examples were provided for each modification type, including descriptions of distinguishing leg features and the species that exhibits that modification.

1. Experiment No: 07
STUDY ON EXTERNAL STRUCTURE OF
INSECT LEG AND IT’S MODIFICATION

2. Leg
• True paired appendages of the thoracic
segments
• Locomotory appendages attached to the
pleural line
• Segmented, cylindrical and more or less
hollow
Fig: A typical insect leg

3. Objectives
• To identify and study the basic parts of
insect leg
• To study the different modification of insect
leg

4. Materials
• Cockroach, Grasshopper, Mole cricket,
Housefly, Honey bee, Praying mantid,
Scavenger beetle
• Compound microscope
• Needle
• Scissors
• Camel hair brush
• Dissecting tray
• Ethyl acetate
• Forceps

5. Procedure
• Anesthetized with ethyl acetate
• Legs detached from body
• Observed under microscope.

6. Functions of Leg
• Locomotion
• Searching of food
• Pollen carrying
• Predation

7. Observation

8. Parts of Leg
• Coxa
• Trochanter
• Femur
• Tibia
• Tarsus
• Pretarsus
Fig: A typical insect leg

9. Modifications of Leg
• Simple walking/running/crusorial type
• Jumping/saltatorial type
• Digging/fossorial type
• Pollen carrying/foragial type
• Grasping/raptorial type
• Swimming/natatorial type
• Clinging/scansorial type
• Legs modified for upside down walking on the
smooth surface

10. Simple Walking Type
• Simple type of leg
• It consists of coxa, trochanter, femur, tibia
and tarsus.
• Femur is greater than tibia.
• Example- Cockroach

11. Fig: Walking type leg
Fig: Cockroach

12. Jumping Type
• Femur is greatly elongated, muscular and adapted for
jumping.
• Coxa and trochanter are relatively smaller in size.
• Tibia spinus.
• Example- Hind leg of grasshopper.
Fig: Walking type leg
Fig: Cockroach

13. Digging Type
• Leg is thick and robust
• Major modification occurs in the tibia
• Tibia is modified into rake like structure
• Tarsi 3 segmented
• Example- Fore leg of mole cricket
Fig: Digging type leg Fig: Mole cricket

14. Pollen Carrying Type
• First segment of the tarsus modified into a pollen
carrying basket
• All the segments bear hairs for carrying pollen
• Example- Honey bee
Fig: Foragial type leg

15. Grasping Type
• Coxa elongated and strong
• Trochanter is very small in size
• Femur and tibia provided with spines for grasping
• Example- Foreleg of prayning mantid.
Fig: Grasping type leg Fig: Praying mantid

16. Swimming Type
• Trochanter very short
• Tarsus provided with numerous hairs for swimming
• Tibia spine hard and long
• Example- Water scavenger beetle.
Fig: Swimming type leg Fig: Scavenger beetle

17. Legs Modified for Upside Down Walking on
the Smooth Surface
• Two prominent claws present
• The pulvillus is provided with hairs, these hairs are
hollow; exude sticky substances which enable the insect
to walk on the smooth surface.
• Example- House fly
Fig: Leg modified for
upside down walking
Fig: House fly