[2] They include the grasshoppers and grasshopper-like insects, as well as other superfamilies classified with them: the ground-hoppers (Tetrigoidea) and pygmy mole crickets (Tridactyloidea).

The phylogeny of the Caelifera, based on mitochondrial ribosomal RNA of thirty-two taxa in six out of seven superfamilies, is shown as a cladogram.

[10][11] [6 superfamilies] Tridactyloidea Tetrigoidea Eumastacidae Proscopiidae Pneumoridae Pyrgomorphidae Acrididae + Pamphagidae In evolutionary terms, the split between the Caelifera and the Ensifera is no more recent than the Permo-Triassic boundary;[12] the earliest insects that are certainly Caeliferans are Eolocustopsis of family Eolocustopsidae from the latest Permian (Changhsingian) of the Beaufort Group, South Africa,[13] followed by Locustavidae and Dzhajloutshellidae from the mid-Triassic (Ladinian age), roughly 242 to 237 million years ago.

The first modern families such as the Eumastacidae, Tetrigidae and Tridactylidae appeared in the Cretaceous, though some insects that might belong to the last two of these groups are found in the early Jurassic.

[16][17] Morphological classification is difficult because many taxa have converged towards a common habitat type; recent taxonomists have concentrated on the internal genitalia, especially those of the male.

The Caelifera have a predominantly tropical distribution with fewer species known from temperate zones, but most of the superfamilies have representatives worldwide.