The wing of an insect and the wing of a bird are said to be analogous because they

Explanation

Both are used for flight, but a bird wing is a modified vertebrate forelimb with bone inside while an insect wing is an outgrowth of the body wall with no bone at all, so the resemblance is functional only. This is convergent evolution, in which unrelated groups meeting the same environmental demand arrive at similar solutions. Analogy therefore tells us about the environment, whereas homology tells us about ancestry.