From Lexicanum

Winged, or Wings ², is a Tyranid biomorph. The forelimbs of some Tyranid creatures have mutated into large leathery wings to allow the creature to move swiftly over long distances by flying, swooping or gliding.² Some creatures also have more than one set of wings or a lightened exo-skeleton.¹

Sources

• ¹:Codex: Tyranids (4th Edition), p.33
• ²: Codex: Tyranids (5th Edition), p.84