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Insect Anatomy and Metamorphosis

External Anatomy of Insects

  • Orders
    • 9-10 major orders of insects.
    • Each order exhibits adaptations that help define it.

Types of Metamorphosis in Insects

  • Three Types of Metamorphosis:

    • Ametabolous (No Metamorphosis):

    • Juveniles resemble tiny adults.

    • Examples:

      • Collembola (Springtails): Tiny, wingless; equipped with a furcula for jumping; found in soil, leaf litter; feed on fungi and decaying matter.
      • Diplura (Bristletails): Long cerci (tails); no eyes; inhabit moist soil; act as scavengers/predators.
      • Zygentoma (Silverfish): Flat, silvery; possess 3 tail filaments; usually found indoors or under rocks, feed on starches.

    • Hemimetabolous (Incomplete Metamorphosis):

    • Nymphs resemble adults and typically share similar habitats.

    • Examples:

      • Ephemeroptera (Mayflies): Characterized by 3 long tail filaments; aquatic nymphs filter feed; short-lived adults.
      • Odonata (Dragonflies/Damselflies): Large eyes, strong wings; gilled aquatic nymphs act as aquatic predators; adults are aerial hunters.
      • Plecoptera (Stoneflies): Soft bodies with 2 cerci; indicate good water quality; inhabit cold, oxygen-rich streams.
      • Hemiptera (True Bugs): Possess piercing-sucking mouthparts; feed on plants; utilize camouflage and mimicry for survival.
      • Orthoptera (Grasshoppers and Crickets): Notable hind legs for jumping; skilled at sound production; found in grasslands; employ camouflage and herbivory.
      • Blattodea (Cockroaches): Flat bodies, long antennae; known for being fast runners; nocturnal scavengers, highly resilient.
      • Mantodea (Mantids): Equipped with raptorial forelegs; act as sit-and-wait predators; excellent camouflage.

    • Holometabolous (Complete Metamorphosis):

    • Involves distinct life stages: larva → pupa → adult; larvae often occupy different environments than adults.

    • Examples:

      • Diptera (Flies): Possess one pair of wings and halteres; have sponging/sucking mouthparts; larvae thrive in decaying matter or water.
      • Lepidoptera (Butterflies, Moths): Characterized by scaled wings; coiled proboscis; larvae (caterpillars) feed on vegetation; adults are nectar feeders.
      • Coleoptera (Beetles): Feature hardened wing covers (elytra); have chewing mouthparts; represent the most diverse group exploiting various food sources.
      • Hymenoptera (Bees, Wasps, Ants): Have two wings; possess chewing and sucking mouthparts; are critical pollinators and exhibit social behavior as colony builders.

Other Arthropod Classes Not Included in Insect Orders

  • Arachnida (Spiders):
    • Characteristics: 8 legs, no antennae, two body parts; utilize webs, venom, and ambush tactics for survival.
  • Malacostraca (Pill Bugs):
    • Seven pairs of legs; segmented bodies; able to roll into a ball; prefer moist environments.
  • Chilopoda (Centipedes):
    • Possess one pair of legs per segment; fast predators equipped with venomous claws.
  • Diplopoda (Millipedes):
    • Have two pairs of legs per segment; move slowly; secrete chemicals as a defense mechanism.