legs modification

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.
a)Eye brush: hairs present on tibia . It is used to
clean compound eyes.
b)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.

22. Thank you!!!!!!!