The document summarizes the structure and segmentation of the insect body. It is divided into three main parts: 1. The head, which is formed from the fusion of seven segments and contains the mouthparts, eyes, and antennae. 2. The thorax, which is composed of three segments - prothorax, mesothorax, and metathorax. Each segment contains a dorsal notum, lateral pleuron, and ventral sternum. The mesothorax and metathorax make up the pterothorax which bears the wings. 3. The abdomen, consisting of 9-11 segments. Each segment contains a dorsal tergum and ventral sternum

1. Organisation of Insect Body
Structure of Head, Thorax and
Abdomen
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2. Insect body segmentation means external
division or grouping the segments into
distinct regions which is called as Tagmosis
Body regions are called as tagmata.
Insect body is divided into three regions
1. Head
2. Thorax
3. Abdomen
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Segmentation of Insect Body

3. This is the first anterior tagma formed by
the fusion of seven segments.
Labral, antennary, ocular, intercalary,
mandibular, maxillary and labial segments.
Head is attached to thorax by cervix.
Head capsule is sclerotized excluding the
place of appendages and formed by
several sclerites (5) known as cranium
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1. Head

4. 5 sclerites in insect head
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1. Head
 Vertex Summit of head between
compound eyes
 Frons Area below vertex and above
clypeus
 Clypeus Cranial area below the frons
where labrum is attached
 Gena Lateral cranial area behind eyes
 Occiput Area between occipital and
post occipital suture

6. Sutures/ Sulcus of Head : Linear invaginations of exoskeleton between two sclerites
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1. Head
 Epicranial suture (Ecdysal line)  Inverted Y shaped suture found mediallyon
the top of head [Median suture (coronal),
Lateral sutures (Frontal)]
 Epistomal suture
(Fronto clypeal)
 Epi: Above ; Stoma: mouth
 Between frons and clypeus
 Clypeo-labral suture  Between clypeus and labrum
 Frontogenal suture  It starts from the junction of the
clypofrontal and the subgenal sutures.

7. Sutures/ Sulcus of Head : Linear invaginations of exoskeleton between two sclerites
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1. Head
 Occipital suture  It is ‘U’ shaped or horseshoe shaped suture between
epicranium and occiput.
 Post occipital
suture
 Groove bordering the occipital foramen
 Line indicating fusion of maxillary and labial segment
 Genal suture  Lateral side of the head i.e. gena
 Occular suture  circular suture present around each compound eye
 Antennal suture  Marginal depressed ring around the antennal socket.

8. Posterior opening of cranium through which
aorta, foregut and ventral nerve cord, neck
muscles passes is known as occipital foramen
Endoskeleton of head cuticle (Tentorium)
provides space for attachment of muscles of
antenna and mouthparts
The appendages like pair of compound eyes,
ocelli, pair of antenna and mouth parts are
called as cephalic appendages
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1. Head

9. Based on the inclination of long axis of head and
orientation of mouthparts there are three types of
insect head
a. Hypognathous (Hypo: Below; Gnathous: Jaw)
Otherwise known as orthopteroid type.
Long axis of head is vertical and right angle to long
axis of body.
Ventrally placed mouth parts projected downwards.
Example: Grasshopper, cockroach
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1. Head

10. b. Prognathous (Pro: infront)
Otherwise known as coleopteroid type.
Long axis of head is horizontal and in the line with
long axis of body. Forwardly directed mouth.
Example: Beetles
c. Opisthognathous (Opistho: Behind)
Otherwise known as hemipteroid type.
Head is deflexed. Moiuthparts are directed
backwards and held between forelegs.
Examples: Bugs @Bhubanananda Adhikari
1. Head

11. Functions of head
Food ingestion
Sensory perception
Coordination of body activity
Protection of coordinating centers
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1. Head

12. Second and middle tagma which is three
segmented namely prothorax, mesothorax and
metathorax.
Main function of thorax is locomotion
Meso and meta thorax which bears wings are
called as pterothorax.
Thoracic segments are made up of three
sclerites.
a). Dorsal plate : Tergum/ Notum
b). Lateral plate : Pleuron
c). Ventral plate : sternum
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2. Thorax

13. Second and middle tagma which is three
segmented namely prothorax, mesothorax
and metathorax.
Meso and meta thorax which bears wings
are called as pterothorax.
Thoracic segments are made upof three
sclerites.
a). Dorsal plate : Tergum/ Notum
b). Lateral plate : Pleuron
c). Ventral plate : sternum
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2. Thorax

14. Thoracic nota:
Dorsal body plate of each thoracic segments are called as
pronotum, mesonotum and metanotum
i. Pronotum :
Undifferentiated (Saddle shaped in grasshopper and
shield like in cockroach
i. Pterothoracic notum:
Three sutures (Antecostal, prescutal, scutoscutellar)
Five tergites( Acrotergite, prescutum, scutum, scutellum,
post scutellum)
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2. Thorax

15. Thoracic pleura:
Pleuralplate is divided into anterior
episternum and posterior epimeron by
pleural suture
Pterothoracic pleuron provides space for
articulation of legs and wings.
Two pairs of spiracles present in
mesopleuron and meta pleuron
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2. Thorax

16. Thoracic sterna:
Ventral body plate (Prosternum, mesosternum
and metasternum)
Thoracic sterna is made up of a segmental
plate called eusternum and intersternite is
called spinasternum
Eusternum is made up of 3 sternites i.e,
presternum, basisternum and sternellum.
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2. Thorax

17. Third tagma made up of 9-11 uromeres
and is highly flexible. Abdominal
segments are telescopic and connected
by conjunctiva
Each abdominal segments made up of 2
sclerites tergum and sternum.
Eight and ninth segments bear female
genital structure, ninth segment bears
male genital structure
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3. Abdomen

18. Thank You…