Trichoptera and several other insect orders have evolved functional diptery while retaining four wings (morphological tetraptery), which results from the interaction of specialized structures that unite the wings. In this contribution, the comparative and functional morphology of the forewing-hindwing coupling apparatuses and related structures in the suborder Integripalpia are presented. The components of the wing coupling apparatuses have varied and complex morphologies and interaction modes, that result in partial to complete wing coupling. Wing coupling has evolved repeatedly within the infraorders Brevitentoria and Plenitentoria, and the morphologies of the wing coupling apparatuses are synapomorphies for several families. Phylogenetic trends are discussed that relate to the evolution of functional diptery, such as the diminution of forewing jugal lobes and hindwing prehumeral setae, reinforcement of wing veins, changes in vein topology and elaboration of wing surface features. A novel at-rest forewing-forewing coupling apparatus that has also evolved repeatedly is described and related to the evolution of wing coupling.