The wings of a butterfly and the wings of a bat cannot be considered homologous because though the function of wings in both the cases is same, but they have different basic design. The butterfly has a fold of membranes as wings which are associated with few muscles but has no bones whereas the wings of bat are supported by bones.
Homologous organs are defined as the organs of different animals that are having a similar structure but differ in their functions. The structure of the two different animals resemble, but the functions of their organs vary. The forelimbs of frogs, a lizard, a bird and a man can have a basic design of bones, but they perform different functions.