Specimen collected under a mature linden tree (Tilia sp.) in a suburban back yard around noontime; probably final instar before pupation, based on size. Very similar characteristics to tomato/tobacco hornworm caterpillar (Manduca sexta?) with a few notable exceptions: General coloration is paler than aforementioned species; "Horn" on posterior end is same color as body; lateral diagonal markings lack red or black color; there is a regular, raised dorsal ridge that runs the entire length of the body (best seen in image #2); and there are two pairs of stubby, spiny "horns" located just behind the head. Any ideas as to what species of Manduca this is?