Hexapods

• Members of the subphylum Hexapoda are named for the presence of six legs.
• All legs of Hexapods are uniramous.
• Hexapods have 3 tagmata: head, thorax and abdomen
• Appendages attach to head and thorax
• There are two classes within Hexapoda: Entognatha and Insecta
• Entognathans are a small group characterized by having the bases of mouthparts enclosed within the head capsule.
• There are three orders within Class Entognathans: Protura, Diplura, and Collembola
• Protura and Diplura are tiny, eyeless, and inhabit soils or dark, damp places.
• Collembola are commonly called springtails because of ability to leap.
• Insecta is an enormous class whose members have ectognathous mouthparts
• In ectognathous mouthparts, bases of mouthparts lie outside the head capsule
• Insects are the most diverse and abundant of all arthropods.
• There are 26 orders within Class Insecta
• Most insects are terrestrial or inhabit freshwater
• Insects are found in nearly all habitats except the sea.
• Insects are common in freshwater, brackish water, and salt marshes.
• Insects are abundant in soils, forest canopies, and can be found in deserts and wastelands.
• Most animals and plants have insects as parasites externally and internally.
• Flight and small size makes insects widely distributed.
• Well-protected insect eggs withstand rigorous conditions and are readily dispersed.
• Insects have 3 tagmata: head, thorax, and abdomen
• Insects have 3 pairs of legs and usually 2 pairs of wings on their thorax.
• Insect head consists of compound eyes, one pair antennae, 3 ocelli, mouthparts (including mandibles & maxillae)
• Insect thorax consists of 3 segments each with a pair of legs, the last 2 segments usually have wings as well.
• Insect abdomen consists of 9 to 11 segments
• Antennae of insects can act as tactile organs, olfactory organs, and sometimes auditory organs.
• Legs of Insects have also become highly specialized for walking, grasping, skating over water, and specialized jobs like gathering pollen.
• Land beetles are thick and shielded.
• Aquatic beetles are streamlined.
• Cockroaches are flat and live in crevices.
• Flight is one key to the great success of insects.
• Insects are the only invertebrates that can fly.
• Insect wings not homologous with bird and flying mammal wings.
• Insect wings are outgrowths of cuticle from the mesothoracic and metathoracic segments.
• Most insects have two pairs of wings.
• Silverfish are ancestrally wingless
• Fleas are secondarily wingless
• Recent fossil evidence suggests insects may have evolved fully functional wings over 400 million years ago.
• Wings for flight are thin and membranous.
• The thick and horny front wings of beetles are protective.