TYPES OF INSECT LEGS

Structure and types of insect legs and identification of insect legs, Modification in insect legs - Cursorial leg(running leg), Ambulatorial leg(walking leg), Saltatorial leg(jumping leg), Scansorial leg(climbing leg), Fossorial leg(digging leg), Natatorial leg(swimming leg), Raptorial leg(grasping leg), Basket – like leg, Sticking leg, Foragial leg, Prolegs or False legs or Pseudolegs

1. AEN 201 FUNDAMENTALS OF ENTOMOLOGY(2+1) TYPES OF INSECT LEGS Submitted by., JAYASANKAR.P B.Sc ., Agriculture

2. Structure The three thorax segments viz., pro-, meso - and metathorax bear a pair of segmented legs. Each leg consists of five segments viz., coxa trochanter femur Tibia tarsus

3. General structure

4. Coxa It is the first or proximal leg segment. It articulates with the cup like depression on the thoracic pleuron . Attached to the body coxa

5. Trochanter It is the second leg segment. It is usually small and single segmented. Trochanter seems to be two segmented in dragonfly, dameselfy . The apparent second trochanter is in fact a part of femur, which is called trochantellus .

6. Femur: It is third segment . Largest segment. Fixed to trochanter . Tibia: It is usually long and provided with downward projecting spines which aid in climbing and footing. Tibia of many insects is armed with large movable spur near the apex.

7. Tarsus: It is further sub-divided. The sub segment of the tarsus is called tarsomere . The basal tarsal segment is often larger than others and is named as basitarsus . Pretarsus : It is a terminal segment. It contain claws. In diptera , it consists of a membranous pulvilli .

8. Modification in insect legs Cursorial leg (running leg): Coxa swollen. Femer -not swollen but elongated. All the segments are slender. Eg ., cockroach.

9. Ambulatorial leg(walking leg) Femur and tibia – long, slender and equal sized. Eg ., fore and middle leg of grasshopper.

10. Saltatorial leg(jumping leg) Coxa -enlarged. Trochanter -small fused with femer . Femer -enlarged, rigid. Tibia – have some spines. Eg ., grasshopper.

11. Scansorial leg(climbing leg) Tibia – stout and bears a thumb – like process at one side. Tarsus – single segmented with a large claw. Eg ., All legs of head louse.

12. Fossorial leg(digging leg) Fore leg – very short and broad. Femur-stout Tibia-short and stout with 2 or 3 strongly pointed tines distally. Tarsus- first 2 segment are produced into strong tines. Eg ., forelegs – mole cricket , dung roller.

13. Natatorial leg(swimming leg) Femur,tibia and first 4 tarsomeres – all broad, flattened, their edges are provided with flattened setae. Eg ., water beetle.

14. Raptorial leg(grasping leg) Coxa – long and mobile. Femur – large, grooved along ventral surface with spines on opposing surface. Tibia – spiny fits into femoral groove. Eg ., forelegs of preying mantis.

15. Basket – like leg Situated just behind the head and are anterior in position. Spiny and closely placed. Eg ., legs of dragonfly and damselfly.

16. Sticking leg All the three pairs of legs of house fly.

17. Foragial leg Adapted for collection of food materials. Eg ., worker bee legs. Fore leg : it has eye brush ,antenna cleaner and pollen brush. Eye brush : hairs present on tibia . It is used to clean compound eyes. Pollen brush : bristles are present on basitrarsus to form pollen brush.

18. Middle leg : it consists of pollen brush and tibial spur. a. Pollen brush : which is useful to collect pollen from middle part of their body. b. Tibial spar: At the distal end of the tibia, a movable spur is present which is useful to loosen the pellets of pollen from the pollen basket of hind legs and to clean wings and spiracles.

19. a. Pollen basket : It is also called corbicula . The outer surface of the hind tibia contains a shallow cavity. The edges of the cavity are fringed with long hairs. The pollen basket enables the bee to carry a larger load of pollen and propolis from the field to the hive. Hind leg: It has three important structures viz., pollen basket, pollen packer and pollen comb.

20. b. Pollen packer : It is also called pollen press. It consists of pecten and auricle. Pecten is a row of stout bristles at the distal end of tibia. Auricle is a small plate fringed with hairs at the basal end of basitarsus . Pollen packer is useful to load pollen in corbicula . c. Pollen comb : About ten rows of stiff spines are present on the inner side of hind basitarsus . The pollen comb is used to collect pollen from middle legs and from posterior part of the body.

21. Prolegs or False legs or Pseudolegs : e.g. abdominal legs of caterpillar. There are two to five pairs of abdominal legs termed prolegs in caterpillar. Prolegs are thick, fleshy and not segmented. They are shed with last larval moult . One pair of prolegs on the last abdominal segment are called anal prolegs or claspers.

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