A hemipteran bug. Many hemipterans are important to humans because they attack crops. All hemiptera have piercing mouthparts which are formed by the mandibles and maxillae which are sheathed in the labium. The whole sructure is called the rostrum, it is normally held underneath the body when the insect is not feeding. The order Hemiptera is divided into two sub-orders; the Heteroptera and the Homoptera. The main differences between the two sub-orders is the wing structure and the rostrum.