BSc 1st year

1. R.K. PANSE
Assistant Professor (Entomology)
College of Agriculture, Balaghat
Murjhad Farm Waraseoni
Email: rkpanse_jnkvv@yahoo.com
rkpanseento@gmail.com
Mobile No. : 9806145992
Lecture no. 10
STRUCTURE AND MODIFICATIONS OF
INSECT LEG

2. Legs
• Three pairs of true legs on three thoracic
segments viz., pro-, meso- and metathorax
• Each leg consists of five segments
- coxa
- trochanter
- femur
- tibia
- tarsus
• Adapted for various modifications for various
functions

3. Structure of Leg
Coxa
Trochanter
Pretarsus
Tersomeres
Tersal claws
Arolium

4. Coxa
It is the first or proximal leg segment.
It is a tubular, broad, triangular or oval shaped.
It articulates with the cup like depression on the thoracic
pleuron.
It is generally freely movable.
Trochanter
It is the second leg segment.
It is usually small and single triangular segmented.
Trochanter two segmented in dragonfly and dameselfy.
The second trochanter is called trochantellus.
Femur
It is 3rd segment
It is the largest and stoutest part of the leg and is closely
attached to the trochanter.
It is highly developed for jumping.

5. Tibia
 It is 4th segment of leg.
 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.
 Femoro-tebia joint is commonly known as the knee of
insect leg.
Tarsus
 It is 5th segment.
 It is furthur divided in to 1-6 segments, each sub-
segment called telomeres.
 The basal tarsal segment is often larger than others and
is named as basitarsus.

6. Structure of Leg
Coxa
Trochanter
Pretarsus
Tersomeres
Tersal claws
Arolium

7. Types or Modifications of Legs
Ambulatorial: (Ambulate - to walk)
e.g. Fore leg and middle leg of
grasshopper. Femur and tibia are
long.
Purpose: Walking
Cursorial: (Cursorial = running)
e.g. All the three pairs of legs of
cockroach. Femur is not swollen.
Purpose: Running

8. Saltatorial: (Salatorial = Leaping)
e.g. hind leg of grasshopper. Femur
and tibia elongated
Purpose: Jumping
Scansorial: (Scansorial = Climbing)
e.g. all the three pairs of legs of head
louse.
Purpose: Climbing

9. Fossorial: (Forrorial = Digging)
e.g. Fore legs of mole cricket. Tibia
and tarsus short and broad with
teeth like projections
Purpose: Digging
Raptorial: (Raptorial = Grasping)
e.g. Forelegs of preying mantis.
femur spine and possess a central
longitudinal groove. Tibia narrow,
blade like spinse and fits into the
groove of femur
Purpose: Holding

10. Natatorial: (Natatorial = swimming)
e.g. hind legs of water bug and water
beetle.
Purpose: Swimming
Clasping leg: e.g. Forelegs of male
water beetle.
Purpose: Clasping

11. Prehensile or Basket: In Dragon
flies the thoracic segments are
obliquely arranged. Tergal plates
pushed backward, whereas sternal
plates pulled forward. As a result
all the legs which are attached to
sternal plates came forwards and
are seen below the head – All the
legs together form a basket like
structure useful for catching the
prey.
Sticking leg: e.g. all the three
pairs of legs of house fly.

12. Foragial leg: (Forage = to collect food
material)
e.g. Legs of honey bee. All three legs
goes to modifying-
Forelegs : 3 important structures
a. Eye brush
b. Antenna cleaner
c. Pollen brush
Middle legs: two structures.
a. Pollen brush: Stiff hairs on basitarsus form
pollen brush which is useful to collect pollen
from middle part of body.
b. Tibial spar: At the distal end of the tibia, a
movable spur is present which is useful to
clean wings and spiracles.

13. Hind legs: three important structures
a. Pollen basket (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.
b. Pollen packer (pollen press): It consists of pecten & 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: 10 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.

14. 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. The tip of proleg is called planta
upon which are borne hooks or claws known as crochets
which are useful in crawling or clinging to surface.