Why do some entomologists classify Homoptera and Heteroptera as suborders of Hemiptera?

Some entomologists classify Homoptera and Heteroptera as suborders of the order Hemiptera primarily because these insects share similar piercing-sucking mouthparts and undergo a similar type of gradual metamorphosis. This classification emphasizes the common evolutionary origin of these groups, suggesting they are closely related to each other and distinct from other insects that lack these specific mouthpart modifications.12

However, this system is a subject of debate. Critics argue that it places only minor importance on significant structural differences, such as the arrangement of the beak and the texture of the wings. For instance, in Heteroptera, the beak is movable and arises from the front of the head, whereas in Homoptera, it is rigidly fixed and appears to arise from the underside. Furthermore, the forewings of heteropterans are divided into leathery basal and membranous apical portions, while homopteran wings are generally of a uniform texture. Because these distinct characteristics have been evolving since the Permian period, some researchers advocate for elevating these groups to separate ordinal ranks.12