Although prawns and grasshopper belong to Arthropoda, they are placed in different classes. Prawns are Crustaceans while grasshopper belongs to Hexapoda (insects). Prawns are aquatic organisms, while grasshopper inhabits terrestrial areas. Crustaceans possess appendages branched at the end, while insects have unbranched appendages. Crustaceans have two pairs of antennae, while insects have one pair of these structures. Crustaceans use gills while insects use the tracheal system for respiration. As a result, these structural and ecological characteristics are used for the separation of prawns and grasshopper into different classes of Arthropoda.