Characteristics: Subclass Pterygota and Its Subdivisions

The subclass Pterygota includes most of the world’s insect species. Pterygota means “wings,” and describes insects that have wings, or once had wings in their evolutionary history. These insects also undergo metamorphosis. The subclass is further divided into two groups – the Exopterygota and the Endopterygota. These are described below.

Insects in this group undergo a simple or incomplete metamorphosis. The life cycle includes just three stages – egg, nymph, and adult. During the nymph stage, gradual change occurs until the nymph resembles the adult. Only the final molt stage has functional wings.

A large number of familiar insects fall within the superorder Exopterygota. There are sixteen orders in this subdivision, including:

• Order Odonata - Dragonflies and Damselflies
• Order Orthoptera - Crickets, Grasshoppers and Locusts
• Order Dictyoptera - Roaches and Mantids
• Order Hemiptera - True Bugs
• Order Thysanoptera - Thrips

These insects undergo a complete metamorphosis with four stages – egg, larva, pupa, and adult. The pupal stage is inactive (a rest period). When the adult emerges from the pupal stage, it has functional wings.

The majority of the world's insects undergo complete metamorphosis, and are included in the superorder Endopterygota. The largest of these nine insect orders are:

• Order Coleoptera - Beetles
• Order Diptera - True Flies
• Order Lepidoptera - Butterflies and Moths
• Order Hymenoptera - Ants, Bees, and Wasps