The original hardback edition of Invaders of Earth was published in 1952 and it featured 22 short stories about alien invasion, all of which had been written between 1907 and 1952. When Pocket Books published a paperback edition in 1955, seven stories were cut for space. The cover above is for the paperback edition and was done by Morton Roberts. I think the three humans featured on the cover are meant to be imprisoned, though it looks like it would be an easy prison from which to escape. The red sky that always seemed to accompany any alien invasion in the 50s is present in the background.
Invaders of Earth was just one of the 40 science fiction anthologies that Groff Conklin edited. Along with writing sci-fi himself, Conklin was also a poet and an author of home improvement books.