Insect Mouthparts Here is a closeup of a grasshopper's mouthparts. You can see how ancestral appendages (legs) have been modified by natural selection to the function of food processing. The ancestral segments that held these appendages have fused to form the grasshopper's head. The front mouthparts, once appendages on the left and right side, have also fused together to form central flaps (the CLYPEUS and the LABRUM) to hold the food in place while it is chewed and swallowed. This is a good example of EXAPTATION, the use of pre-existing body parts with one function as raw material for the evolutionary development of new functions.