Grasshoppers have a typical insect nervous system, and have an extensive set of external sense organs. On the side of the head are a pair of large compound eyes which give a broad field of vision and can detect movement, shape, colour and distance. There are also three simple eyes ('ocelli') on the forehead which can detect light intensity, a pair of antennae containing olfactory (smell) and touch receptors, and mouthparts containing gustatory (taste) receptors.

At the front end of the abdomen there is a pair of tympanal organs for sound reception. There are numerous fine hairs ('setae') covering the whole body that act as mechanoreceptors (touch and wind sensors), and these are most dense on the antennae, the 'palps' (part of the mouth), and on the 'cerci' at the tip of the abdomen.

There are special receptors ('campaniform sensillae') embedded in the cuticle of the legs that sense pressure and cuticle distortion. There are internal 'chordotonal' sense organs specialized to detect position and movement about the joints of the exoskeleton. The receptors convey information to the central nervous system through sensory neurons, and most of these have their cell bodies located in the periphery near the receptor site itself.

Grasshoppers are typically ground-dwelling insects with powerful hind legs which allow them to escape from threats by leaping vigorously.

More Info: en.wikipedia.org