• Order Orthoptera

  Hindlegs almost always enlarged and adapted for jumping; tarsi usually 3- or 4-segmented, occasionally fewer than 3 or as many as 5 segments; front wings more or less thickened; wing pads reversed (hindwing partly covering front wing) during late nymphal stages; cerci nearly always unsegmented; specialized auditory and stridulatory organs often present.

  • Suborder Ensifera

    Antennae usually long, with more than 30 segments; auditory organs, if present, consist of tympanum at base of front tibia; many species with stridulatory mechanism at base of tegmen; ovipositor usually present as rounded or flattened bladelike, or elongated cylindrical spearlike, structure.

    • Superfamily Hagloidea

      Tarsi compressed or cylindrical, 3- or 4-segmented; tympanum present; simple stridulatory vein on each male tegmen.

      • Family Prophalangopsidae

        Triassic to present. 25–47 mm in size; recent species found in India and northwestern North America; 3 species.

    • Superfamily Tettigonioidea

      Tarsi usually depressed, 4-segmented, at least on middle and hind legs; tympanum present; stridulatory organ specialized, with left tegmen uppermost and scraper (at edge of lower tegmen) often better developed on right tegmen.

      • Family Tettigoniidae (katydids, bush crickets)

        Jurassic to present; size range from 15 to 120 mm, average about 35 mm; distribution worldwide; about 3,000 species.

        • Subfamily Phasmodinae; (phasmodids)

          Very slender; head prognathous (i.e., mouth directed forward instead of downward); hind femurs not enlarged; all members recent; found in Australia; size range from 25 to 85 mm; 2 species.

    • Superfamily Stenopelmatoidea

      Tarsi depressed, usually 4-segmented; front wings without stridulatory mechanism; usually no tympanum; ovipositor usually flattened, bladelike; 12 to 50 mm in size with average 25 mm.

      • Family Stenopelmatidae (stenopelmatids, Jerusalem crickets)

        Heavy body, often wingless, with front legs usually strongly armed for digging; ovipositor inconspicuous; represented from Miocene to present; members found in southeastern Asia, Southern Africa, North America, and Central America; about 35 species.

      • Family Gryllacrididae (raspy crickets and leaf-rolling grasshoppers)

        Usually wingless or with vestigial wings; found from Jurassic to present; chiefly tropical, most nocturnal, in trees and shrubs.

      • Family Schizodactylidae (schizodactylids)

        Winged or wingless; when winged, wing tips very long, rolled in a coil at rest; tarsal segments 2 and 3 with conspicuous lateral lobes; all members recent, found in southern Asia, South Africa; about 8 species.

      • Family Rhaphidophoridae (camel crickets and cave crickets)

        Wingless; usually of humpback appearance; tarsi compressed; legs often very long and slender; found from Oligocene to present; worldwide distribution; about 300 species.

      • Family Anostostomatidae

        Usually wingless; front tibia with 1 or more dorsal spurs; front coxa usually with spine; represented in Old and New World tropics; about 150 species.

    • Superfamily Grylloidea

      Tarsi 3-segmented; tegmina of males usually highly developed for stridulation; tympanum usually at base of front tibia; ovipositor most often round in cross section, spearlike, other times somewhat flattened or reduced; 2 to 50 mm in size with average 18 mm.

      • Family Gryllidae (crickets)

        Front legs usually not for digging; ovipositor usually elongated; species from Triassic to present; worldwide distribution; about 2,400 species.

      • Family Gryllotalpidae (mole crickets)

        Front legs highly modified for digging, with tibiae expanded and with fingerlike dactyls; ovipositor vestigial; represented from Oligocene to present; distribution worldwide; about 65 species.

  • Suborder Caelifera

    Antennae short, with less than 30 segments; auditory organs, if present, at base of abdomen in form of tympanum; ovipositor usually consists of paired valvular appendages adapted for digging.

    • Superfamily Tridactyloidea

      Tarsi 1- or 2-segmented; antennae short, with 12 or fewer segments.

      • Family Tridactylidae (pygmy sand crickets)

        Front tarsi 2-segmented; hind tibiae with unsegmented tarsus, no “claws,” 2 long “paddles”; usually winged; 3 to 18 mm in size; worldwide distribution; about 60 species.

      • Family Cylindrachaetidae (false mole crickets)

        Body elongated, cylindrical, wingless; antennae 7- to 8-segmented; eyes reduced; ocelli absent; front tibia with 4 or 5 dactyls; cerci very short. All members recent; inhabit Australia and southern South America; size 40–60 mm; about 8 species.

    • Superfamily Tetrigoidea

      Pronotum strongly elongated, extending backward over most or sometimes all of abdomen; tegmina short, scalelike; hind wings usually fully developed; no tympanum; front and middle tarsi 2-segmented; hind tarsus 3-segmented.

      • Family Tetrigidae (pygmy grasshoppers or grouse locusts)

        Miocene to present; 8–25 mm in size with average about 14 mm; worldwide distribution; about 700 species.

    • Superfamily Eumastacoidea (Superfamily Proscopioidea)

      Abdominal spiracles situated in lateral membrane between terga and sternums; basal abdominal terga without auditory tympanum; basal segment of hind tarsus with serrated margins or at least with an external tubercle (all U.S. species wingless).

      • Family Eumastiacidae (eumastacids or monkey grasshoppers)

        Sides of abdomen without stridulatory organ; antennae relatively short; frontal costa forked below median ocellus; represented from Miocene to present; worldwide in warm countries; about 200 species.

      • Family Proscopiidae (proscopiids)

        All representatives recent; from Costa Rica to southern South America; size 30 to 180 mm with average about 60 mm; about 100 species.

    • Superfamily Tanaoceroidea

      Wingless; basal abdominal terga without auditory tympanum; small to medium in size; antennae notably longer than those of eumastacid species.

      • Family Tanaoceridae (tanaocerids)

        Specialized stridulatory organ on side of 3rd abdominal tergum, rubbed by hind femur; antennae very long; frontal costa not forked; found in southwestern U.S.; 3 species.

    • Superfamily Pneumoroidea

      Body robust; male fully winged, female short winged; hind legs short; tympanum absent; male with stridulatory ridges on side of 3rd abdominal tergum.

      • Family Pneumoridae (pneumorids)

        All members recent; restricted to southern Africa; 11 to 107 mm in size; about 18 species.

    • Superfamily Acridoidea

      Typically robust, with both pairs of wings and tympanum present, although extremely variable; pronotum not or briefly prolonged over abdomen; abdominal spiracles located in terga; tarsi 3-segmented, basal segment without serrated margins; size 8 to 120 mm with average about 28 mm.

      • Family Acrididae (grasshoppers)

        Many of unusual appearance; stridulatory mechanism often present, but not with organ on abdomen; vertex without a definite longitudinal furrow; tympanum normally present (absent in some, especially wingless genera); ocelli small; hind tibiae usually not expanded apically for swimming; Eocene to present; worldwide distribution; more than 5,000 species.

      • Family Pamphagidae (pamphagids)

        Usually large; wings variable; many wingless bulky species in arid regions; vertex of head with longitudinal furrow; lower basal lobe of hind femur longer than upper lobe; members recent; in Africa and southern parts of Europe and Asia; about 300 species.

      • Family Pyrgomorphidae (pyrgomorphids)

        Head conical; longitudinal furrow of vertex present; lower basal lobe of femur longer than upper lobe; tympanum usually present; no stridulatory mechanism; recent; worldwide in tropical and subtropical areas, unknown in U.S.; about 350 species.

Each of the following families contains only a few species: Xyronotidae, Ommexechidae, Trigonopterygidae, Pamphagodidae, Lathiceridae, Lentulidae. The Xyronotidae includes 1 Mexican species only; the other families are not represented in North America.

Critical appraisal

The arrangement of orders, suborders, superfamilies, and families presented above is a consensus of current opinion; however, some entomologists recognize different relationships and additional families too minor or too little understood to be included here. In most large groups, there are a few peculiar species that vary slightly from the characteristics described. Although an attempt was made in this classification to indicate the earliest geologic period in which major groups were found, available information is not always clear as to whether the insect found belongs to a modern family or an ancestral one with more primitive features and a different name. The known species shown for each group represent only living ones that have been named, not fossils. In some cases, modern catalogs and monographs can be used to obtain accurate counts; for other cases, however, estimates are given.