Familiarity with the twenty-nine insect orders is the key to identifying and understanding insects. In this introduction, I have described the insect orders beginning with the most primitive wingless insects, and ending with the insect groups that have undergone the greatest evolutionary change. Most insect order names end in ptera, which comes from the Greek word pteron, meaning wing.
11. Order Dermaptera
Photo: © Susan Ellis, Bugwood.org
This order contains the earwigs, an easily recognized insect that often has pincers at the end of the abdomen. Many earwigs are scavengers, eating both plant and animal matter. The order Dermaptera includes less than 2,000 species.
12. Order Embioptera
The order Embioptera is another ancient order with few species, perhaps less than 200 worldwide. The web spinners have silk glands in their front legs, and weave nests under leaf litter and in tunnels where they live. Web spinners live in tropical or subtropical climates.13. Order Dictyoptera
Photo: yenhoon/Stock.xchng
The order Dictyoptera includes roaches and mantids. Both groups have long, segmented antennae and leathery forewings held tightly against their backs. They undergo incomplete metamorphosis. Worldwide, there approximately 6,000 species in this order, most living in tropical regions.
14. Order Isoptera
Photo: © Susan Ellis, Bugwood.org
Termites feed on wood, and are important decomposers in forest ecosystems. They also feed on wood products, and are thought of as pests for the destruction they cause to man-made structures. There are between 2,000 and 3,000 species in this order.
15. Order Zoraptera
Little is know about the insects in the order Zoraptera. Thought they are grouped with winged insects, many are actually wingless. Members of this group are blind, small, and often found in decaying wood. There are only about 30 described species worldwide.16. Order Psocoptera
Bark lice forage on algae, lichen, and fungus in moist, dark places. Book lice frequent human dwellings, where they feed on book paste and grains. They undergo incomplete metamorphosis. Entomologists have named about 3,200 species in the order Psocoptera.17. Order Mallophaga
Biting lice are ectoparasites that feed on birds and some mammals. There are an estimated 3,000 species in the order Mallophaga, all of which undergo incomplete metamorphosis.18. Order Siphunculata
The order Siphunculata are the sucking lice, which feed on the fresh blood of mammals. Their mouthparts are adapted for sucking or siphoning blood. There are only about 500 species of sucking lice.19. Order Hemiptera
Photo: © Erich G. Vallery, USDA Forest Service - SRS-4552, Bugwood.org
Most people use the term "bugs" to mean insects; an entomologist uses the term to refer to the order Hemiptera. The Hemiptera are the true bugs, and include cicadas, aphids, and spittlebugs, and others. This is a large group of over 70,000 species worldwide.
20. Order Thysanoptera
Photo: © Forestry Archive, Pennsylvania Dept. of Conservation and Natural Resources, Bugwood.org
The thrips of order Thysanoptera are small insects that feed on plant tissue. Many are considered agricultural pests for this reason. Some thrips prey on other small insects as well. This order contains about 5,000 species.
