Agricultural Study Materials

Insect Mouth Parts and their Modifications – Agricultural studies – Free Online Studymaterial

Mouth parts of insects have many variations in structure and function depending upon theirfeeding situations. Insect mouthparts are broadly classified into two groups:-
  1. Mandibulate type (Biting types) (Feeding on solid food)
  2. Haustellate type (Sucking type) (Feeding on liquid food)

I. Mandibulate types1. BITING AND CHEWING TYPEEg.: Cockroach, Grasshopper, Beetles, Larva
  • Labrum: Rectangular plate like
  • Mandibles: A pair of hard teeth like
  • Maxilla: A paired structure containing CARDO and STIPES STIPES bears GALEA, LACINIA AND MAXILLARY PALP
  • Labium: Contains MENTUM, SUBMENTUM and PREMENTUM
  • PREMENTUM bears a pair of GLOSSA, a pair of PARAGLOSSA and LABIAL PALP
  • Hypopharynx: Muscular elongation present in the middle of the mouth

Function: Mandibles are used for biting and maxilla are used for chewingII. Haustellate type    The mouth parts of insects which feed on fluids are modified in various ways to form tubethrough which liquid can be drawn into the mouth. The muscles of the cibarium or pharynx arestrongly developed to form a pump. There are different types:-2. PIERCING AND SUCKING TYPEEg.: Plant bug ( 4 stylets), Mosquitoes ( 6 stylets)
 
  • Labrum: Hook like
  • Mandibles: Modified into two sharp needles called STYLETS
  • Maxilla: Modified into two sharp needles called STYLETS
  • Labium: Modified into 3 – 4 segmented PROBOSIS / ROSTRUM
  • Hypopharynx: Modified as a STYLET in mosquitoes along with labrum
  • Function: Mandibles pierces tissue and maxilla sucks up the juice in plant bug

    Mandibles & maxilla pierces the skin, hypopharynx & labrum sucks up blood (In mosquitoes)3. CHEWING AND LAPPING TYPEEg.: Honeybees
  • Labrum: Semicircular
  • Mandibles: Club shaped
  • Maxilla: GALEA alone is visible and enlarged. Its inner surface is conclave
  • Labium: GLOSSA is enlarged and LABIAL PALP is present
  • Function: Galea forms a roof over glossa and this structure forms lapping tongue

Mandibles are used for chewing and moulting wax.4. SPONGING TYPEEg: Housefly
  • Labrum: Absent
  • Mandibles: Absent
  • Maxilla: Reduced
  • Labium: Modified into elbowed fleshy PROBOSCIS with spongy tip namely LABELLUM possessing many grooves called PSEUDOTRACHEAE
  • Hypopharynx: Forms food channel along with labrum
  • Function: Labellum is pressed upon the food as a sponge and juice is collected Via Pseudotracheae.

5. CUTTING AND SPONGING TYPEEg: Horsefly
  • Labrum: Absent
  • Mandibles: Modified as sharp blade
  • Maxilla: Modified as sharp style
  • Labium: Modified into elbowed fleshy PROBOSCIS with spongy tip namely LABELLUM possessing many grooves called PSEUDOTRACHEAE
  • Hypopharynx: Absent
  • Function: Mandibles and maxilla cut open the skin and labellum sponges the oozing blood.

6. SIPHONING TYPEEg: Butterflies and Moths
  • Labrum: Reduced
  • Mandibles: Absent
  • Maxilla: Galea is elongated into lengthy tube called PROBOSCIS
  • Labium: Labial palp alone visible
  • Hypopharynx: Absent
  • Function: Proboscis is coiled like watch spring while at rest and protruded whilesiphoning nectar from flowers.

7. RASPING AND SUCKING TYPEEg: Thrips
  • Labrum: Modified as stylet
  • Mandibles: Right mandible reduced; Left mandible modified as stylet Hence, it is called as ASYMMETRICAL MOUTHPARTS
  • Maxilla: Modified as stylet
  • Labium: Forms the mouth cone
  • Hypopharynx: Modified as stylet
  • Function: The mandibulary and maxillary stylets rasp the leaf surface,Hypopharynx and labrum sucks up the oozing liquid.

8. MANDIBULOSUCTORIAL TYPEEg: Antlion
  • Labrum: Absent
  • Mandibles: Long, Slender, Sickle shaped with central groove.
  • Maxilla: Slender, covers up the groove of the mandible
  • Labium: Absent
  • Hypopharynx: Absent
  • Function: Sickle shaped mandibles pierce the body and sucks up the body fluids

9. Mouth parts of immature forms

    Besides the above types, in case of naiads of dragonflies and damselflies, the labium is enlargedand elbow shaped. The apical portion of the prementum bears a pairs of grasping jaws. At rest,the extended elbow of the labium is kept flexed over the mouth parts which form the “mask”.    When the prey reaches the striking range, the labium is exerted out suddenly and the jaws graspthe prey and retract back for feeding. In case of larval mosquitoes, the mouthparts arerepresented by small hairy structure that act as filter. Many other flies have a well-developed,vertically moving mouth hooks as feeding organs.

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