The Sternorrhyncha suborder of the Hemiptera contains the aphids, whiteflies, and scale insects, groups which were traditionally included in the order Homoptera. "Sternorrhyncha" refers to the rearward position of the mouthparts relative to the head. Distributed worldwide, all members of this group are plant-feeders (phytophagous), and many are major crop and ornamental pests. Many exhibit modified morphology and/or lifecycles, including phenomena such as flightless morphs, parthenogenesis, sexual dimorphism, and eusociality.