Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada

Class Insecta - Insects

Leafhopper - Macropsis osborni - female Moth BioBlitz Bug 35 - Oecetis Swamp Milkweed Leaf Beetle - Labidomera clivicollis Fallen Oak Leaf Mine ID Request - Stigmella Moth - Dryadaula Arizona Moth - Eucopina franclemonti Presumed Epalpus signifer - Epalpus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Synonyms and other taxonomic changes
phylogenetic arrangement of major extant taxa based on latest molecular data shown in(1)
Explanation of Names
Latin insectum, pl. insecta "cut into, cut up" (refers to body segmentation), a literal translation of Greek entomos (εντομος)
Worldwide, 25-30 extant orders (+ ca. 10 extinct), depending on authority, up to 1000 families, and well over a million species
In our area (US & Canada): 28 orders, over 600 families, ca. 12,500 genera, and >86,000 spp.(2)(3)
Three pairs of legs
Three body parts: head, thorax, and abdomen
typically two pair of wings; some groups have one pair or none
One pair of antennae
Usually one pair of compound eyes; simple eyes (ocelli) present in many groups


See Glossary for terminology.

worldwide and throughout North America (NB: aquatic marine forms conspicuously absent)
Life Cycle
There are two prominent types of life cycles among the insects:
1-Hemimetabolous 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.
2-Holometabolous insects have a four-stage life cycle: egg, larva, pupa, and adult (imago). The following orders of insects are holometabolous:
Neuroptera - Antlions, Lacewings and Allies
Coleoptera - Beetles
Hymenoptera - Ants, Bees, Wasps and Sawflies
Trichoptera - Caddisflies
Lepidoptera - Butterflies and Moths
Mecoptera - Scorpionflies, Hangingflies and Allies
Diptera - Flies
Strepsiptera - Twisted-winged Insects
Siphonaptera - Fleas
They form a group referred to as Endopterygota or Holometabola.
Print References
Eggleton, P., and Belshaw, R. 1992. Insect Parasitoids: An Evolutionary Overview. Philosophical Transitions of the Royal Society of London B 337: 1-20. doi: 10.1098/rstb.1992.0079
Stork, N. E. 2018. How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth?. Annual Review of Entomology 63: 31-45.
Gaston, K. J. 1991. The Magnitude of Global Insect Species Richness. Conservation Biology 5(3): 283-296.
Works Cited
1.Phylogenomics resolves the timing and pattern of insect evolution
Bernhard Misof et al. 2014. Science Vol. 346, 763.
2.American Insects: A Handbook of the Insects of America North of Mexico
Ross H. Arnett. 2000. CRC Press.
3.Evolution of the Insects
David Grimaldi and Michael S. Engel. 2005.
4.How to Know the Immature Insects
Hung-Fu Chu, Laurence K Cutkomp. 1992. Wm. C. Brown Publishers.