Why do other entomologists treat Homoptera and Heteroptera as separate insect orders?

Some entomologists argue that Homoptera and Heteroptera should be classified as separate insect orders rather than suborders of Hemiptera because they prioritize significant structural and developmental differences over the shared trait of piercing-sucking mouthparts.12

Key reasons for this distinction include:

• Mouthpart Structure: In Heteroptera, the beak is movable and arises from the front of the head. In Homoptera, the beak is rigidly fixed and appears to arise from the underside of the head. Furthermore, homopterans lack the gula—a hard bridge separating mouthparts from the prothorax—which is present in heteropterans.13
• Wing Morphology: Heteropteran forewings are divided into leathery basal and membranous apical sections, held flat at rest. Homopteran forewings are of uniform texture and are held in a rooflike position.1
• Physiological Differences: Homopterans lack the scent glands found in terrestrial and many aquatic heteropterans.3
• Evolutionary History: Distinctive traits, such as the migration of mouthparts to the prothorax, suggest an ancient phylogenetic divergence dating back to the Permian period, supporting their status as separate orders.3