They're nothing more than a hybrid night crawler.
What provoked my interest in it was the comment about how they prefer sandy soil.
In the Sandhills of Nebraska, there live no worms.
I spent my childhood years alongside the Platte River, which of course is black soil, where worms were all over, under the top of the ground. But during my adolesence in the Sandhills, I noticed, oops, no worms.
Night-crawlers of course are the most common form of fish-bait used around here--and there is considerable fishing around here--but they have to be imported from.....Canada, and cost $3.59 a dozen.