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External Anatomy II Lecture 11

External Anatomy II Lecture 11. Segmentation and tagmosis. 6. 3. 11. Insect body is divided into a series of segments, the metameres , which are grouped into three distinct regions or tagmata : head, thorax, and abdomen. Tagmosis : amalgamation of segments into functional units.

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External Anatomy II Lecture 11

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  1. External Anatomy IILecture 11

  2. Segmentation and tagmosis 6 3 11 • Insect body is divided into a series of segments, the metameres, which are grouped into three distinct regions or tagmata: head, thorax, and abdomen. • Tagmosis: amalgamation of segments into functional units

  3. Primary vs. Secondary Segmentation • Primary segmentation: • Found in non-arthropod protostomessuch as Annelida • Externally visible grooves in the body wall serve as muscle attachment • Secondary segmentation: • Found in arthropods • Externally visible segmentation does not conform to internal muscle attachment

  4. Major body axis

  5. Sclerite: a plate on the body wall surrounded by membrane or sutures Tergum: dorsal plate, tergite Sternum: ventral plate, sternite Pleuron: side plate, pleurite (membrane in abdomen, sclerotized in thorax)

  6. Abdomen: • Obviously segmental • 11 segments (with various reductions in different insects) • Pregenital segments - First 7 abdominal segments; similar in structure • Genital segments - abdominal segments 8 and 9 • Postgenital segments - abdominal segments 10 and 11 • Abdominal segment 11 bears a pair of cerci Grasshopper Fly

  7. Thorax: • Three segments – prothorax, mesothorax, metathorax • Mesothorax + methorax = pterothorax (wing bearing) • Each thoracic segment bears a pair of legs

  8. Dorsal view Ventral view Cross section

  9. Legs: • Fore legs (prothorax), Mid Legs (mesothorax), and Hind Legs (metathorax) • Coxa + trochanter + femur + tibia + tarsus + pretarsus • Tarsus + pretarsus– several components (tarsomere, pulvili, tarsal claws, arolium), one muscle

  10. Leg movement is determined by articulation of different segments • Coxa – 1 or 2 articulations • Trochanter – 2 articulations • Femur – 2 articulations • Tibia – 2 articulations • Tarsus – 1 articulation

  11. Wings: • Fore wings (mesothorax), Hind wings (metathorax) • 8 Major veins: precosta (PC), costa (C), subcosta (Sc), radius (R), media (M), cubitus (Cu), anal (A), and jugal (J) • Veins contain tracheae, blood vessels, nerve fibers • Cross vein – provide support • Pterostigma – opaque or pigmented spot, assist in gliding

  12. Main areas of a wing • Remigium: powered by thoracic muscles • Clavus: anal area + jugal area • Fold-lines: along which wing can be folded • Flexion-lines: at which wings flexes during flight • Axillary area: muscle attachment site

  13. Head: • Consists of 6 fused segments • preantennal (ocular) • antennal • labral • mandibular • maxillary • labial • Consists of two functional units • cephalic sensory • mouthparts

  14. Posterior view Internal view The rigidity of the head is increased by four apodemes that meet internally to form a brace for the head, known as the tentorium.

  15. Mouthparts: • formed from appendages of head segments 3-6 • five basic components • Labrum (segment 3) • Hypopharynx (origin uncertain) • Mandibles (segment 4) • Maxillae (segment 5) • Labium (segment 6) # sensilla (# chemosensitive neurons)

  16. Cephalic sensory structures: • Compound eyes – vision • Ocelli – light/dark sensor • Antennae – olfactory, tactile, movement

  17. Antennae: • All insects have a pair • Protura is the only hexapod without antennae • Consist of scape, pedicel, and flagellum • Insect antennae are annulated (no muscle in flagellum) Segmented (Collembola, Diplura) Annulated (insects only)

  18. Insects have evolved for more than 350 million years resulting in: • Diverse biology & ecology • Diverse morphology

  19. Modification of abdomen Moth Ichneumon wasp Katydid

  20. Modification of legs digging grasping grooming pollen collecting raptorial

  21. Modification of wings elytron tegmen hemelytron haltere

  22. Modification of mouthparts Butterfly Mosquito Honey bee

  23. Modification of antennae Moniliform Clavate Filiform Serrate Pectinate Flabellate Plumose Aristate Geniculate

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