In ornithology, the winglet, bastard wing, or ala spuria of a bird; the packet of small feathers which grows upon the so-called thumb of a bird's wing.In entomology: The small membranous appendage or scale situated at the base of each wing of many dipterous insects, above the halteres or poisers.A similar appendage beneath each elytron of some water-beetles. Also called alulet and cucilleron.