The insect head contains compound eyes, simple eyes, mouthparts, and antennae. It is formed by the fusion of six segments and can be divided into two regions: the procephalon and gnathocephalon. The head is attached to the thorax by the neck/cervix region. There are three basic head orientations in insects: hypognathous heads have mouthparts directed downward, prognathous heads have mouthparts directed forward as seen in carnivores, and ophisthognathous heads have an elongated proboscis sloping backwards.

1. Lecture no. 6
Body segmentation: Structure of head &
its types
R K PANSE
Assistant Professor
Entomology

2. Insect Structure

3. Body Segmentation
 3 body regions
 1 pair of antennae
 3 pair of legs on the thorax
 2 pair of wings on the thorax
Head
Thorax
Abdomen

4. Head: The head is the feeding and sensory centre. First anterior
tagma formed by the fusion of six segments namely
preantennary, antennary, intercalary, mandibular, maxillary and
labial segments. The head segments can be divided in to two
regions i.e. procephalon and gnathocephalon (mouth).
Segments Regions Appendages
I Pre antennary segment
Procephalon
No appendages
II Antennary segment Antennae
III Intercalary segment No appendages
IV Mandibular segment
Gnathocephalon
Mandible
V First maxillary segment Maxillae
VI Second maxillary / labial segment Labium

5. Head is attached or articulated to the thorax through neck or
cervix. Head capsule is sclerotized and the head capsule
excluding appendages formed by the fusion of several sclerites
is known as cranium.
The insect head is a capsule that contains a pair of compound eyes, a
pair of simple eyes (ocelli), mouth parts and a pair of antennae.

6. Sclerites of Head
Cuticular plates or areas which are joined together
i. Vertex: Summit of the head between compound eyes.
ii. Frons: Facial area below the vertex and above clypeus.
iii. Clypeus: Cranial area below the frons to which labrum is
attached.
iv. Labrum : It is small
sclerite that forms the
upper lip of the mouth
cavity.
v. Gena: Lateral cranial
area behind the compound
eyes.
Post gena-sclerites below
the genae and above the
mandibles.

7. vi. Occiput : Cranial area between occipital and post occipital
suture.
Post occiput : It is the extreme posterior part of the insect
head that remains before the neck region.
Occular sclerites : These are cuticular ring like structures
present around each compound eye
10. Antennal sclerites : These form the basis for the antennae
and present around the scape which are well developed in
Plecoptera (stone flies)

8. Sutures of Head: The linear invaginations of the exoskeleton
between two sclerites are called as suture or sulcus.
i. Epicranial suture/ ecdysial line: Inverted `Y' shaped suture
found medially on the top of head, with a median suture (coronal
suture) and lateral sutures (frontal suture).
ii. Epistomal suture/ Fronto clypeal suture: Found between frons
and clypeus.
iii. Clypeo-labral suture: Found between clypeus and labrum.
Iv Genal suture: Lies on either
side of the head below the
compound eyes separating facial
part from gena.
v. Sub-genal suture: A line
below the gena on either side of
the head.
vi. Occipital suture: line
between occiput & post occiput.
vii. Postoccipital suture:

9. Types of head
Orientation of Head: with respect to the rest of the body axis.
Insects have three basic types of head viz.,
• Hypognathous (the mouthparts are directed downward, with the
mouth parts in a continous series with the legs, is a primitive type.
This orientation mostly occurs in vegetarian speciaes living in
open habitats.

10. Prognathous (the mouthparts are directed forward and this is
found in carnivores species which actively pursue their prey, and
in larvae, particularly of coleopteran, which use their mandible
for burrowing).

11. Ophisthognathous (the elongated proboscis slopes
backwards between the front legs, e.g. Hemiptera and
Homoptera).