1. BODY WALL OR INTAGUMENT
OF INSECT
PRESENTED BY
Dr. Sachin Kumar Jaiswal
(Department of Entomology)
2. BODYW
ALLOR INTEGUMENT OFINSECT
• Insect body wall is called as Exoskeleton.
• It is the external covering of the
body which is ectodermal in origin.
• It is rigid, flexible, lighter, stronger and variously
modified in different body parts to suit different
modes of life.
• Serves as a protective covering over the body,
also know integument.
3. The insect integument consisting of
1. The cuticle
2. The epidermis or hypodermis
3. The basement membrane
Fig: General structure of insect body wall
4. • It is outermost thick layer of integument.
• It is complex and non cellular layer.
• Secreted by epidermis.
• When newly formed it is flexible and elastic.
• When under goes sclerotization it becomes hardened
and darkened.
1. The cuticle
5. • A. The Epicuticle (Upper layer of epicuticle)
• B. The Exocuticle (Middle layer of epicuticle)
• C. The Endocuticle (Lower layer of epicuticle)
* The exocuticle and the endocuticle jointly
called as Procuticle
Sub layer of Cuticle
6. A. The Epicuticle
• It is very thin outer most layer.
• Thickness : 0.03 – 4.00 micron.
• Chitin is absent in epicuticle.
• It consists of following 4 layers
• Cement layer
• Wax layer
• Polyphenol layer
• Cuticulin layer
7.
8. (1). Cement layer
• Secreted by dermal gland.
• Composed of lipoprotein.
• It is less than 0.1 µ thick.
• It protects the body from external damage.
9. (2). Wax layer
• Prominent layer
• Thickness - 0.25 micron
• Consisting of long chain hydrocarbons, esters of
fatty acids and alcohols.
• It is secreted by epidermal cell.
• It serves as water proof layer
• Preventing water loss from the body.
10. (3). Polyphenol layer
• It is non-static layer
• Containing various type of phenols which are mainly
used in the formation of proteins.
• It is secreted by epidermal cells
• Resistant to acids and organic solvents.
11. (4). Cuticulin layer
• It is amber colure thin layer
• It is secreted by oenocytes
• Serves the purpose of permeability and Act as
growth barrier.
12. • Exocuticle
• Darkly pigmented, hard and sclerotized
• Sheded during ecdysis with the exuvium
• Consisting mainly chitin and hard protein called
Sclerotin.
• Endocuticle
• Light colored
• Soft and unsclerotized
• Consisting more chitin
• Lack of hard protein Sclerotin.
• Digested by active moulting fluid
B. Procuticle
13. 2. Epidermis
• Unicellular layer formed from polygonal cells
• Modified into cuboidal or columnar during the
moulting.
• Consists of well developed nucleus and other
cytoplasmic contents.
• Adjacent epidermal cells are held together by means
of certain cytoplasmic processes which are known as
desmosomes.
• It is single layer of cells lying below the cuticle.
• Secretes greater part of cuticle and moulting fluid
14. • The epidermal cells get differentiated in to
following types based on the function they perform
and may modify into
• (a) Dermal glands producing cement layer
• (b)Trichogen cell producing hair like seta or trichome.
• (c) Moulting glands secreting moulting
fluid which digests the old cuticle
• (d) Peristigmatic glands around the
spiracles in case of Dipteran larvae.
15. Function of Epidermis
• Epidermis resting on basement with the membrane
following function.
• Cuticle secretion
• Digestion and absorption of old cuticle
• Wound repairing
• Gives surface look
16. 3. Basement membrane
• Basal part of the body wall formed from degenerated
epidermal cells.
• Appear as non-living amorphous (shapeless) granular
layer.
• About 0.5μ in thickness and consists of fibrous
protein, glycos-amino-glycans which are polymers of
disaccharides.
• Forms a continuous sheet beneath the
epidermis, where muscles are attached and become
continuous with sarcolemma of the muscles.
17. Function of body wall
It provides the Structure, size and shape of the insect body.
It conserve moisture and prevent desiccation.
It protects the insect organs against physical harm.
It provides the space for muscle attachment.
It helps to prevent the entry of
harmful microbes and chemicals.
It serves as interface between insect and environment.
It helps to maintain an ionic balance in insect body.
It serves as the site of sensory input.
It acts as external armour and strengthen external organs like
jaws and ovipositor
It Internally
trachea.
protects the vital organs, foregut, hindgut and
It contains pigment to make insect attractive
18. Process and appendages of the body wall
/Integument and their structure
The outer surface of the cuticle of the insects is
very rarely smooth or bare, but bears a variety
of fine microscopic roughening in the form of
ridges, tufts, hairs etc. The outgrowth of
the body wall can be broadly classified into
two groups
1.Internal processes
2.External processes
20. 1. Internal processes
• These occur in the form of invagination of the body
wall. It is providing space for muscle attachment and
also known as endoskeleton. There are two types
a. Apodeme: Hollow invagination of body wall
(ridge like).
b. Apophysis: Solid invagination of body wall (spine
like).
21. • Apodemes may be plate or arm like and
definitely have a mechanical function. They
strengthen the exoskeleton by forming a brace.
They also furnish space for attachment of muscles.
Fine slender thread like apodemes are known as
“tendons”.
apophysis
22. 2. External processes
• The external processes of the body wall may be in
the form of hairs, spines, setae or scales. These
external processes may again be sub divided into two
types:-
• A. Non cellular process
• B. Cellular process
23. A. Non cellular process
• The non cellular processes of the body wall are
purely cuticular structure, not epidermal
association but rigidly attached. They may be in
the form of corrugations, ridges or nodules, small
spines, hairs etc.
24. Microtrichia
(1) Microtrichia / fixed hairs / aculei: These are minute
hair like structures found on wings of
Mecoptera and certain Diptera.
(2) Spines: Outgrowths of the cuticle which are
more or less thorn like in form.
25. B. Cellular processes
• The cellular processes have epidermal association and
it may be classified into unicellular and multicellular
processes or appendages.
• a. Unicellular
• b. Multicellular
26. a. Unicellular process
• These are typical outgrowths of the body wall and
consists of hair like processes known as “setae”.
• Setae arise from a cup like alveolus or pit.
• Its are hollow structures produced by a single
enlarged epidermal cell called ‘ trichogen’ cell.
• Articular membrane is usually produced by a second
epidermal cell called ‘tormogen’ cell.
• Study of arrangement of seta is known as
Chaetotaxy.
28. Different kinds of setae are as follows
a. Clothing hairs, plumose hairs. e.g. Honey bee.
b. Bristles. e.g. flies.
c. Scales - flattened out growth of body wall e.g.
Moths and butterflies
d. Glandular seta. e.g. caterpillar
e. Sensory setae - associated with sensory neuron or
neurons
f. Poison setae – slug caterpillar
29. (a) Clothing hairs
• These are hair like structures that
cover body, legs and wings. e.g: honey
bee
the entire
30. (b) Scales
• These are highly modified clothing hairs and are
unicellular, pigmented, small flat scale like structures
covering the body as well as wings of adult
moths and butterflies. Each scale are arises as
a blunt process of a special trichogen cell of the
wing or body epidermis. Initially it is a small bag like
in shape and later flatters out.
32. (c) Glandular setae
• Setae that functions as outlet for the secretion of
epidermal glands. If they are especially stout and
rigid, they are called glandular bristles, as in case of
certain larvae of Lepidoptera.
33. (d) Sensory setae
• These are the setae or trichomes provided with
sensory receptors or sensory nerve cells
and respond to the external stimuli.
These are present on antennae, legs and
mouth parts.
34. (e) Poison setae
• The larvae of certain Lepidoptera, belong to families
Noctuidae, Arctidae, Nymphalidae etc. process
a special poison gland cell attached with the
trichogen cell. They discharge their venom when
the tip is broken off. In this the seta has been
carried out the end of the spine and the poison
gland cell is also found just below its base.
36. b. Multicellular processes
• Hallow out growths of the entire body wall
• Lined by epidermal cells.
• Usually large and spine like in form.
They may be again of the two types:-
• Fixed or immovable: Spine
• Movable: Spur
• The fixed or immovable type of processes are termed
as spine, and are present on the hind tibia of
Orthoptera (Grasshopper and locust). Multicellular spines
with poison gland cell are present in some Lepidoptera
insects.
• Spurs are the movable processes and present at the end of
tibia.
