Scala Iterator with Map and For

Given:

val list = List("one","two","three")     
val it = list.toIterator

I can run:

list map ("_" +) -> List(_one, _two, _three)
for (i <- list) yield("_" + i) -> List(_one, _two, _three)

If I run the same on the iterator I get:

it map ("_" + ) -> Iterator[java.lang.String] = empty iterator
for (i <- it) yield("_" + i) -> Iterator[java.lang.String] = empty iterator

Shouldn't I get back another (non-empty) Iterator[String] after I run map/for on it?