Alimentary canal Foregut Midgut Hindgut Salivary glands Types Composition of Saliva Regulation Functions of salivary glands

1. INSECT DIGESTIVE SYSTEMS-
ASSOCIATED GLANDS AND
THEIR FUNCTIONS

2. Index
• Introduction-Alimentary canal
• Associated glands
1. Mandibular glands
2. Maxillary glands
3. Hypopharyngeal gland
4. Labial gland/Salivary glands
5. Other glands-
o Poison,Dufour’s,Antennal,Defensive gland

3. Insect digestive system

4. pharynx
esophagus crop
Malpighian tubules
salivary glands
mouth
salivarium
Gastric caeca
gizzard
ileum
rectum
ventriculus
anus
FOREGUT MIDGUT HINDGUT
Foregut
• Preoral cavity
• Pharynx
• Oesophagus
• Crop
• Proventriculus
Midgut
• Gastric caeca
• Malpighian tubules
Hindgut
• Ileum
• Colon
• Rectum

6. 1.Mandibular Glands
• Str.-sac like;opens near the base of
mandibles.
• Found in Apterygota , Blattodea ,
Mantodea , Isoptera , Coleptera ,
Hymenoptera and Lepidoptera
larvae.
• Function-1.In hymenopterans,
mandibular glands excrete alarm
pheromones .
2. In Lepidoptera larvae
they function as salivary glands.

7. 2.Maxillary glands
• Opens near the bases of
maxillae.
• Found in- Protura and
Collembola, and in
some larval Neuroptera
and Hymenoptera.
• Function- lubrication of
mouthparts .

8. 3.Hypopharyngeal glands
• Occur in pair.Ducts open at the base of hypopharynx.
• Found in-Hymenoptera, like honey bees.
• Function-In addition to the salivary enzymes they
produce, these glands also yield secretions to feed
the larvae.

9. 4.Labial glands(Salivary
glands)
• Most common gland.
• Are present in all insects, except in Coleoptera.
• Resides in thorax.
salivary glands
salivarium

10. Two types
1. Acinar –
• Sac-like ;present in most insects.
• Regulated by nervous system
• -Eg-Orthoptera

11. 2. Tubular –
• Tubular structure.
• Regulated by serotonin in
haemolymph.
• Found in Diptera ,
Lepidoptera,Siphonaptera

12. Composition
• Depends on diet of insect.
• Consist of-
1. Amylase-Converts Starch to Maltose
2. Invertase-Converts Sucrose to Glucose and
fructose
3. Lipase-Converts Fat to fatty acid and glycerol
4. Pectinase-present in saliva of Aphids.
5. Anticoagulants-present in saliva
of blood sucking insects.

13. Subesophageal
ganglion
Stomatogastric NS
Regulation
1. Acinous glands-By stomatogastric system and
subesophagal ganglion
2. Tubular glands-By serotonin.

14. Functions of Salivary Glands
1. Moisten mouthparts
and serves as a
lubricant
2. Act as food solvent.
3. Contains digestive
enzymes.
4. Silk production in larva
of Lepidoptera and
Hymenoptera.

15. 5.Other glands
1. Poison and Dufour’s
gland-
• Associated with sting
apparatus in female
Hymenoptera.
• Function-Poison gland-
venom delivery system
-Dufour’s gland-
secrete trail pheromone.

16. 2. Antennal glands
• Found in many beetles.
• Opening on surface of antenna.
• Function-1.Serves to lubricate the joints.
2.Secretes antimicrobial
secretions.
3. Defensive glands
• Found in some rove beetles.
• Present on abdomen.
• Function-Stimulates ants in carrying
them to their nests and taking care
of them.