Grasshoppers have the typical insect body plan of head, thorax and abdomen. The head is held vertically, at an angle to the body with the mouth at the bottom. It bears a large pair of compound eyes which give all-round vision, three simple eyes which can detect light and dark and a pair of antennae which are sensitive to touch and smell. The downward-directed mouthparts are modified for chewing and there are two sensory palps in front of the jaws.
The thorax and abdomen are segmented and have a rigid cuticle made up of overlapping plates composed of chitin. The three fused thoracic segments bear three pairs of legs and two pairs of wings. The forewings, known as tegmina, are narrow and leathery while the hind wings are large and membranous, the veins providing strength. The legs are terminated by claws for gripping. The hind leg is particularly powerful; the femur is robust and has several ridges where different surfaces join and the inner ridges bear stridulatory pegs in some species. The posterior edge of the tibia bears a double row of spines and there are a pair of articulated spurs near its lower end. The interior of the thorax houses the muscles that control the limbs.
The abdomen has eleven segments, the first of which is fused to the thorax and contains the auditory organ and tympanum. Segments two to eight are ring-shaped and joined by flexible membranes. Segments nine to eleven are reduced; segment nine bears a pair of cerci and segments ten and eleven house the reproductive organs. Female grasshoppers are normally larger than males, with short ovipositors.
Those species that make easily heard noises usually do so by rubbing a row of pegs on the hind femurs against the edges of the forewings (stridulation). These sounds are produced mainly by males to attract females, though in some species the females also stridulate.
Grasshoppers are easily confused with the other sub-order of Orthoptera, Ensifera (crickets), but differ in many aspects, such as the number of segments in their antennae and structure of the ovipositor, as well as the location of the tympana and modes of sound production. Ensiferans have antennae that can be much longer than the body and have at least 20–24 segments, while caeliferans have fewer segments in their shorter, stouter antennae.