The type species of
Amorpha Hubner, 1809 is
juglandis; the species was originally placed in the genus
Sphinx.
The type species of
Laothoe is
populi, an Old World species originally placed in the genus
Sphinx.
Laothoe is an
Old World genus that apparently does not occur in North America. (the "Amorpha" referred to in the previous two links was Hubner's
rejected name for the Old World
Sphinx populi in 1806, not Hubner's
accepted name for the North American
Sphinx juglandis in 1809).
The listing of a "Laothoe juglandis" on many web sites is presumably an error, as the species
juglandis has never been formally placed in the genus
Laothoe, according to the synonym history shown at
FUNET.