Insect mouthparts

Modification of insect mouthparts

1. Structure and modifications of mouthparts Prepared by Dr. S. Sumaiya

2. 1. Chewing Mouth Parts Represent the simplest type of mouth parts Occure in silverfish, grasshopper, cockrocaches , beetle, dragonflies, bird lice and caterpillars Biting off, chewing and swallowing small bits from plant and animal tissues. Labrum, mandibles, First maxillae, Second maxillae, Hypopharynx

3. Labrum Broad somewhat rectangular, vertical plate It forms anterior wall of the preoral cavity Called upper lip Flap like, bilobed and attached to clypeus Pull the food Labrum epipharynx (Inner surface) – organ of taste

4. Mandibles Heavily sclerotized triangular st.lying just behind the labrum on the side of preoral cavity. They bear strong pointed teeth Work horizontally to cut and chew the food Two types: Distal -sharply pointed – Incisor or cutting Proximal teeth – Molar or Grinding Primary jaws or True jaws

5. Maxillae Lie behind the mandibles also on side of the preoral cavity. Consist of ( i ) a basal protopodite of two segment 1. Cardo 2. Stipes 3. Palpifer 4. Mxillary palp (5 segments) (ii) An inner endopodite also two segment 1. Lacinia (jaw like) 2. Galea (hood like) Hold the food when mandibles are in action - Mastication

6. Labium Lie behind the Ist maxillae, form hind wall of the preoral cavity. Called lower lip. Divided into 3 sclerites : Submentum , mentum and prementum Lateral side of pre mentum : two small lateral sclerites – Palpiger – 3 segmented labial palpi Distally – outer : Paraglossae Inner : Glossae Both when fuse : Ligula

7. Hypopharynx Short, median, tongue like chitinous st . located just in front of the labium and b/w the Ist maxillae. Comprises two lobes called superlinguae . Salivary duct opens at its base.

8. 2.Chewing –lapping Mouth Part Occur in worker bees. Used for collecting nectar and moulding wax. Labrum and mandibles are chewing type, maxillae and labium are modified to form lapping tongue for collecting nectar. Mandibles are smooth and blunt, these mould the wax to build cells of hive. The tongue consists of 2 galea of maxillae 2 labial palpi of labium Glossa – circular spoon shape : bouton or flabellum

9. 3.Piercing-Sucking Mouth Parts Occur in bug, aphids, scale insects, mosquitoes, fleas, some flies. Pierce into the plant or animal tissue, suck sap or blood from it. Sub types ( i ) Dipterous mouth parts (ii) Hemipterous mouth parts

10. Dipterous Mouth Parts Found in Female mosquitoes. Form long ,pointed stylets for piercing the host skin. Hypopharynx encloses the salivary duct. Maxillary palps are shot and 3 –jointed. Labium – elongated, Grooved forming a gutter which encloses 6 stylets Saw like - Piercing Antocoagulant - Anesthetic

11. Hemipterous Mouth Parts Found in bugs. Mandibles and maxillae form 4 long, needle like piercing stylets . Hypopharynx is short lobe . Maxillary and labial palps are absent. The tip of the stylets has minute teeth for piercing the host plant. Labium - into beak or rostrum, which is elongate and sheathlike , four segmented, front ( Hemiptera ) or rear ( Homoptera ) of the head. Labium acts - protective covering (fascicle) At the base of the labium, there is a triangular flap-like structure called labrum.

12. Rasping-sucking Intermediate in chewing type and piercing- Sucking type. Found in thrips (Mouth cone) Form 3 stylets – 2 maxillae & Left mandible (Right – Absent) Maxillary palp and labial palp is present

13. 5. Sponging/lapping Mouth parts Occur in housefly, blow flies, fruit flies. Absorbing fluid food, solid food is first liquified by salivary secretion Mandibles are absent, maxillae reduced to single palp Proboscis 3 parts:- i ) rostum ii) haustellum iii) suction pad Suction pads/ sponging organ – oral discs or labella Surface of labella transversed – capillary canals - Pseudotrachea

14. Siphoning Mouth Parts Occur in butterflies and moth . Sucking tube or Proboscis – two galea of maxillae – interlocking – spines/ hooks The proboscis is coiled up and kept beneath the head – not in use Labial palpi and maxillary palpi present

15. Mandibulo-suctorial type ( Antlion grub) Mandibles - long, curved (sickle-shaped) - groove on their inner surface. Each maxilla is elongated and fits against the mandibular groove to form a channel which is used to suck the sap.