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Class Insecta - Insects
Classification Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Class Insecta (Insects)
Explanation of Names From Latin insectum (plural insecta) for "cut into, cut up". This refers to the way the joints between body segments are marked by an indentation as if carved by a chisel. The word probably arose as a literal translation of Greek entomos (εντομος), which has the same meaning. Numbers 29 orders (mantids and cockroaches in separate orders here)
949 families
Over 1 million species
28 orders
612 recorded families
12,428 recorded genera
86,346 recorded species
Nearctica lists 34 orders. Identification Three pairs of legs
Three body parts: head, thorax, and abdomen
None, one, or two pair of wings
One pair of antennae
Usually one pair of compound eyes
Anatomy
See figure: 
See BugGuide Glossary for terminology. Life Cycle Hemimetabolus insects (e.g., dragonflies, mayflies, true bugs, grasshoppers) undergo gradual, or incomplete, metamorphosis. Immature stages (usually called nymphs) go through a series of molts, gradually assuming an adult form. Since the wings develop on the outside of the body, these groups are called exopterygotes. Some orders have immature stages that are aquatic. These possess specialized structures for aquatic life, such as gills, and are called naiads, or larvae. Remarks Pterygota--winged insects--was formerly considered a subclass of Insecta--see the linked glossary entry for more information.
Note on taxonomic sequence of insects
The sequence of orders of winged insects used in BugGuide follows, mostly, that used in Arnett, American Insects (2). There has been some disagreement about the sequence of orders in Insecta presented here. It has been the consensus both in the 2006 discussion and the 2007 discussion NOT to use an alphabetical sequence for the orders, because this places related groups far apart. Please discuss before making changes. As an organizational aid, see the alphabetical list below.
Alphabetic list of Pterygota orders
Dictyoptera - Mantids and Cockroaches
Hymenoptera - Ants, Bees, Wasps and Sawflies
Hemiptera - True Bugs, Cicadas, Hoppers, Aphids and Allies
Lepidoptera - Butterflies and Moths
Mallophaga - Chewing Lice
Mecoptera - Scorpionflies, Hangingflies and Allies
Neuroptera - Antlions, Lacewings and Allies
Odonata - Dragonflies and Damselflies
Orthoptera - Grasshoppers, Crickets, Katydids
Phasmatodea - Walkingsticks
Psocoptera - Barklice and Booklice
Strepsiptera - Twisted-winged Insects
Trichoptera - Caddisflies
Print References Wilson, Animal: The Definitive Visual Guide to the World's Wildlife (1)
Arnett, American Insects, p. xvii--sequence of insect orders (2)
Bland and Jacques, p. 64 (3)
Borror and White, page 56 (4)
Castner, Photographic Atlas of Entomology (5)Internet References North Carolina State University: General Entomology--excellent site with systematics, descriptions, images.
Insect Morphology - a primer for beginners, University of Sydney
Australian National Museum: What is an Insect?
Tree of Life-- Insecta, Pterygota
Insects of Cedar Creek-- Taxonomic Survey--shows Arnett's sequence of orders
Works Cited | 3. | How to Know the Insects
By Roger G. Bland, H.E. Jaques |  |
| 4. | A Field Guide to Insects
By Richard E. White, Donald J. Borror, Roger Tory Peterson |  |
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