A Guide to the 29 Insect Orders

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.

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Order Thysanura

Photo: © Joseph Berger, Bugwood.org

The silverfish and firebrats are found in the order Thysanura. They are wingless insects often found in people's attics, and have a lifespan of several years. There are about 600 species worldwide.

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Order Diplura

Diplurans are the most primitive insect species, with no eyes or wings. They have the unusual ability among insects to regenerate body parts. There are over 400 members of the order Diplura in the world.

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Order Protura

Another very primitive group, the proturans have no eyes, no antennae, and no wings. They are uncommon, with perhaps less than 100 species known.

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Order Collembola

Springtail. Photo: © Flickr user Neil Phillips

The order Collembola includes the springtails, primitive insects without wings. There are approximately 2,000 species of Collembola worldwide.

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Order Ephemeroptera

Photo: © Whitney Cranshaw, Colorado State University, Bugwood.org

The mayflies of order Ephemeroptera are short-lived, and undergo incomplete metamorphosis. The larvae are aquatic, feeding on algae and other plant life. Entomologists have described about 2,100 species worldwide.

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Order Odonata

Photo: © Susan Ellis, Bugwood.org

The order Odonata includes dragonflies and damselflies, which undergo incomplete metamorphosis. They are predators of other insects, even in their immature stage. There are about 5,000 species in the order Odonata.

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Order Plecoptera

Photo: © Whitney Cranshaw, Colorado State University, United States

The stoneflies of order Plecoptera are aquatic and undergo incomplete metamorphosis. The nymphs live under rocks in well flowing streams. Adults are usually seen on the ground along stream and river banks. There are roughly 3,000 species in this group.

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Order Grylloblatodea

Sometimes referred to as "living fossils," the insects of the order Grylloblatodea have changed little from their ancient ancestors. This order is the smallest of all the insect orders, with perhaps only 25 known species living today. Grylloblatodea live at elevations above 1500 ft., and are commonly named ice bugs or rock crawlers.

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Order Orthoptera

Photo: © Whitney Cranshaw, Colorado State University, United States

These are familiar insects - grasshoppers, locusts, katydids, and crickets - and one of the largest orders of herbivorous insects. Many species in the order Orthoptera can produce and detect sounds. Approximately 20,000 species exist in this group.

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Order Phasmida

Photo: © Whitney Cranshaw, Colorado State University, Bugwood.org

The order Phasmida are masters of camouflage - the stick and leaf insects. They undergo incomplete metamorphosis, and feed on leaves. There are some 3,000 insects in this group, but only a small fraction of this number are leaf insects. Stick insects are the longest insects in the world.

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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.

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Order Embiidina

The order Embioptera is another ancient order with few species, perhaps only 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.

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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.

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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.

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Order Zoraptera

Little is know about the angel insects, which belong to the order Zoraptera. Though 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.

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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.

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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.

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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.

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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.

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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.

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Order Neuroptera

Photo: © Johnny N. Dell, Retired, United States

Commonly called the order of lacewings, this group actually includes a variety of other insects, too: dobsonflies, owlflies, mantidflies, antlions, snakeflies, and alderflies. Insects in the order Neuroptera undergo complete metamorphosis. Worldwide, there are over 5,500 species in this group.

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Order Mecoptera

Photo: © Haruta Ovidiu, University of Oradea, Bugwood.org

This order includes the scorpionflies, which live in moist, wooded habitats. Scorpionflies are omnivorous in both their larval and adult forms. The larva are caterpillar-like. There are less than 500 described species in the order Mecoptera.

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Order Siphonaptera

A female Xenopsylla cheopis flea, vector of plague. Photo: World Health Organization

Pet lovers fear insects in the order Siphonaptera - the fleas. Fleas are blood-sucking ectoparasites that feed on mammals, and rarely, birds. There are well over 2,000 species of fleas in the world.

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Order Coleoptera

Photo: © Debbie Hadley, WILD Jersey

This group, the beetles and weevils, is the largest order in the insect world, with over 300,000 distinct species known. The order Coleoptera includes well-known families: june beetles, lady beetles, click beetles, and fireflies. All have hardened forewings that fold over the abdomen to protect the delicate hindwings used for flight.

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Order Strepsiptera

Insects in this group are parasites of other insects, particularly bees, grasshoppers, and the true bugs. The immature Strepsiptera lies in wait on a flower, and quickly burrows into any host insect that comes along. Strepsiptera undergo complete metamorphosis, and pupate within the host insect's body.

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Order Diptera

Photo: © Whitney Cranshaw, Colorado State University, Bugwood.org

Diptera is one of the largest orders, with nearly 100,000 insects named to the order. These are the true flies, mosquitoes, and gnats. Insects in this group have modified hindwings which are used for balance during flight. The forewings function as the propellers for flying.

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Order Lepidoptera

Photo: Gerald J. Lenhard, Bugwood.org

The butterflies and moths of the order Lepidoptera comprise the second largest group in the class Insecta. These well-known insects have scaly wings with interesting colors and patterns. You can often identify an insect in this order just by the wing shape and color.

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Order Trichoptera

Photo: Jessica Lawrence, Eurofins Agroscience Services, Bugwood.org

Caddisflies are nocturnal as adults, and aquatic when immature. The caddisfly adults have silky hairs on their wings and body, which is a key to identifying a Trichoptera member. The larvae spin traps for prey with silk. They also make cases from the silk and other materials which they carry and use for protection.

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Order Hymenoptera

Photo: © Whitney Cranshaw, Colorado State University, Bugwood.org

The order Hymenoptera includes many of the most common insects - ants, bees, and wasps. The larvae of some wasps cause trees to form galls, which then provides food for the immature wasps. Other wasps are parasitic, living in caterpillars, beetles, or even aphids. This is the third largest insect order with just over 100,000 species.