Subphylum Hexapoda (Six Legs)

    Class Insecta

        (Latin Insectum coming from the Greek Entomon - Cut into segments) (Entomologists study insects)

Insect Characteristics

      -Mandibles - Mouth appendages exposed and projected from head

      -Exoskeleton made of Chitin

      -Have a 3 part body (Head, thorax, and abdomen)

      -Have six legs (Hexapoda)

      -Are the most diverse group of animals on earth

      -Make up 90% of all diverse species on this planet

      -Probably somewhere between 6 and 10 million species (Only one million named so far)

      -The only invertebrates to evolve flight

        -Usually when an animal evolves flight that group of animals evolves to have many species. The group of mammals that has the most species is bats. The reason is if you can fly you can travel and colonize new areas then your colony is subject to natural selection and sexual selection separate of your home colony.  

      -Most species co-evolved with flowering plants

        -Because flowers provide nectar for insects and insects provide pollination to plants they have evolved very specific traits together.

Insects have many different life cycles depending on the species. Many of them go through a type of metamorphosis. Metamorphosis is one way we can classify insects.

There are three types of metamorphosis in insects

    (Metabolous - coming from the word metabolic which is Greek for change)

Ametabolous metamorphosis

        -There is no metamorphosis

        -The juvenile looks exactly like the adult form

Hemimetabolous metamorphosis

        -Partial metamophosis

        -There is an egg-Nymph-adult stage

        -A nymph looks very similar to the adult except it usually does not have wings

        -A nymph goes through a small metamorphosis to become an adult

Holometabolous metamorphosis

        -A complete metamorphosis

        -There is an egg-larva-pupa-adult stage

        -The larva looks completely different than an adult

        -The larva has to create a pupa to turn into the adult stage

            -A moth's pupa stage is a cocoon

            -A butterflies pupa stage is a chrysalis

There are 24 orders of the class Insecta

     Here are some important orders of the Class Insecta:

Ametabolous Insects

     Subclass Apterygota - Insects without wings

          (Greek - A for not or non and Pteron for wing)

     Order Archaeognatha

        -The oldest and least changed order of insects. Evolved only shortly after the arachnids. Is probably the first insects on land. The name archae (old) and Gnatha (jaw) refers to the order only having one mandible when most other insects have two. They have the ability to spring and jump.

        -The jumping bristletails

    Order Thysanura

           -Greek - Thysanos - Bristle and Oura - Tail

           -Very similar to the Archaeognatha except they cannot jump. They eat carbohydrate fibers which leads them to sometimes eat clothing.

           -Silverfish

           -Our oldest insect fossil looks like a silverfish and it dates to 396 million years old

Hemimetabolous Insects

     Subclass Pterygota - Insects with wings

         (Greek - Pteron - Wing)

      Order Odonata

             -Greek - odontos - Tooth (Because they have teeth on their mandibles)

            -Elongate, membranous wings with netlike venation; abdomen long and slender; compound eyes occupy most of the head; hemimetabolous metamorphosis

            -Dragonflies and damselflies

 Infraclass Neoptera- Wings are folded at rest

     Order Mantodea

            -Greek - Mantis - prophet

            -Prothorax long; prothoracic legs long and armed with strong spines for grasping prey; predators; hemimetabolous metamorphosis

            -Mantids

        Order Blattaria

              -Greek and Latin Blatta - cockroach

              -Body oval and flattened; head concealed from above by a shieldlike extension of the prothorax; hemimetaboulous metamorphosis

              -Cockroaches

Dubia Cockroach from Venezuela

        Order Isoptera

              -Greek - Iso same and pteron wing

              -Workers white and wingless; front and hindwings of reproductives of equal size; reproductives and some soldiers may be sclerotized; abdomen broadly joins thorax; social; hemimetaboulous metamorphosis

            -Termites

        Order Dermaptera

              -Greek - Derm Skin and Pteron Wing

              -Elongate; chewing mouthparts; threadlike antennae; abdomen with insegmented forceps like cerci; hemimetabolous metamorphosis

              -Show maternal care and guard their eggs

              -Earwigs

        Order Orthoptera

              -Greek Ortho - straight Pteron - Wing

              -20,000 species

              -Forewing long; narrow, and leathery; hindwing broad and membranous; chewing mouthparts; hemimetabolous metamorphosis

              -Grasshoppers, crickets, katydids

        Order Phasmida

              -Greek - Phasma ghost

              -Body elongate and sticklike; wings reduced or absent; some tropical forms are flattened and leaflike; hemimetabolous metamorphosis

              -Walking sticks, leaf insects

Walking Stick Eggs

        Order Hemiptera (True Bugs)

              -Greek Hemi - half Pteron - wing

              -80,000 species

              -Piercing-sucking mouthparts; mandibles and first maxillae styletlike and lying in grooved labium; wings membranous; hemimetaboulous metamorphosis

              -Bed Bugs, Cicadas, Leafhoppers, Aphids

Holometabolous Insects

        Order Coleoptera

              -Greek Koleos - Sheath Pteron Wing

              -370,000 species

              -Forewings sclerotized, forming covers (elytra) over the abdomen;; hindwings membranous; chewing mouthparts; the largest insect order; holometabolous metamorphosis

              -Beetles

Darkling Beetle (Mill Beetle)

        Order Lepidoptera

               -Greek - Lepis - Sclales Pteron - Wings

               -180,000 Species

               -Wings broad and covered with scales; mouthparts formed into a sucking tube; holometabolous metamorphosis

               -Moths, butterflies

        Order Diptera

              -Greek Di - two Pteron - Wings

              -100,000 species

              -Mesothoracic wings well developed; metathoracic wings reduced to knoblike halteres; variously modified but never chewing mouthparts; holometabolous metamorphosis

             -Flies

        Order Siphonaptera

               -Greek Siphon - to suck Pteron wings

               -100,000 species

               -Laterally flattened, sucking mouthparts; jumping legs; parasites of birds and mammals; holometabolous metamorphosis

               -Fleas, mosquitoes 

       Order Hymenoptera

               -Greek Hymen - membrane Pteron - Wings

               -150,000 Species

               -Wings membranous with few veins; well-developed ovipositor, sometimes modified into a string; mouthparts modified for biting and lapping; social and solitary species; holometabolous metamorphosis

               -Ants, bees, wasps

Double Crossing Ants

Parasitic Wasps

Bumble Bee

Argentine Ants

Leaf Cutter Ants

Videos:

Hawk Moth

Insect Worlds: Them and Us