Insects and their relatives are hexapods, having sixlegs, connected to the thorax, each with five components. In order from the body they are the coxa, trochanter, femur, tibia, and tarsus. Each is a single segment, except the tarsus which can be from three to seven segments, each referred to as a tarsomer Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods but modern arthropods have eight or fewer. It has been argued ^[ that the ancestral leg need not have been so complex, and that other events, such as successive loss of function of a Hox -gene, could result in parallel gains of leg segments.