Speed 0, Fly Speed x, Prone, and Crawling

[Xyrlove Woodsoul]

Perhaps I overlooked something in the Rules Compendium, but say a Hell Wasp Devil (who has a speed of 0, but a fly speed of 8) is knocked prone. I'm guessing that it cannot crawl? Or can it fly-crawl? (so long as it fly-crawls at least 2 squares).

 

[Incenjucar]

It can crawl 0 squares.

Also, when it's not prone, it can still shift 1 square as per usual.

 

[AuraSeer]

If it is knocked prone while flying, it falls. If it has a move action left, or if it hasn't yet hit the ground by its next turn, it can take the "Stand Up" action to right itself.

If it's prone on the ground, and for any reason can't take off again, speed 0 means it can't move anywhere. It can't crawl because crawling only moves you half your speed, and half 0 is still 0. Being prone means it can't even shift to go 1 square.