Help with larvae - south NV

[Mark Walker]

I'm in the higher desert near Goodsprings, NV.  I'm looking at fairly mature
larvae that are devouring a bushy, squatty desert plant with very large
purple blossoms (about the size of a racquetball).  I'm not familiar with
the plant.  The larva appear to be sphingid-like - with a small hook on the
tail end.  At least a few of them are large - a couple of inches.  There are
several color forms - one very dark, and others mostly green.  There are
longitudinal dark bands - two distinct on one of the green larva.

I suppose these could be White-lined Sphinx larvae.  Anything other
suggestions?

Thanks,

Mark Walker
actually, it's the Gold Strike in Jean, NV
Whiskey Pete's is in Primm.