Insecta

Insects are the largest class of Hexapoda, over 75% of all animal species. This huge diversity is linked with vast morphological diversity.

Morphology of insects

Head

Comprised of 6 segments
Antennae made of numerous segments with little differentiation
2 compound eyes and 3 ocelli (single visual unit)

Thorax

Comprised of 3 segments (prothorax, mesothorax, and metathorax)
Prothorax very small
Mesothorax and metathorax sizes depend on the wing size
Legs consist of 5 segments
Wings on meso and metathorax

Abdomen

Comprised of 11 segments but in most species terminal 3 are much reduced
Females have ovipositors on the 8th and 9th segments
Males have claspers on the 9th segment for holding the female during mating

Below are the major subgroups of the Class Insecta.

Class Insecta

Subclass Apterygota

Order Archaeognatha (bristletail)
Order Zygentoma (=Thysanura, silverfish)

Subclass Pterygota

Infraclass Palaeoptera

Order Ephemeroptera (mayflies)
Order Palaeodictyoptera (EXTINCT)
Order Megasecoptera (EXTINCT)
Order Diaphanopterodea (EXTINCT)
Order Protodonata (EXTINCT)
Order Odonata (dragonflies, damselflies)

Infraclass Neoptera

Infraclass Neoptera: Division Exopterygota

Order Plecoptera (stoneflies)
Order Blattodea (cockroaches)
Order Mantodea (praying mantis)
Order Dermaptera (earwigs)
Order Orthoptera (grasshoppers, crickets)
Order Hemiptera (true bugs)
Order Homoptera (cicadas, aphids)
Order Phasmatodea (stick-insects, leaf-insects)
Order Embioptera (web-spinners)
Order Isoptera (termites)
Order Psocoptera (booklice)
Order Phthiraptera (lice)

Infraclass Neoptera: Division Endopterygota

Order Coleoptera (beetles, weevils)
Order Trichoptera (caddis-flies)
Order Neuroptera (lacewings, antlions)
Order Megaloptera (alderflies, dobsonflies)
Order Lepidoptera (butterflies)
Order Hymenoptera (wasps, bees, ants)
Order Diptera (flies, mosquitoes)
Order Strepsiptera (stylops)
Order Siphonaptera (fleas)
Order Mecoptera (scorpion-flies)

Major Subgroups

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