Hawk Moth Caterpillar

My photos were taken this afternoon, rather late, as it was getting dark. So the quality is not quite as it would be in good daylight. I don't remember seeing a Hawk Moth larva with these colours before. So I cannot say much about it at this point, other than to say that it is most definately a Hawk Moth. The first identifier is, of course, the tail horn, but the general shape of this larva, the way it moves and the type and style of its markings all point to it being a Sphingid. The tail horn probably started out much longer (in relation to the body size), but when it appears reduced to a "stub" as in this case, it is usually an indicator of a late instar. That could mean that it has stopped eating and is on the point of pupation, but since I could not be certain of any of this, I made the decision to collect it and keep it in a rearing cage. I felt that if it were not yet on the point of pupation, it would probably die. My reason for thinking that is based on experience. I have observed Hawk Moth larvae, in the past, which had not yet reached the late instar/pre-pupation stage and had no remaining vegetation to eat. They went into pupation anyway, but did not survive, presumably due to lack of nutritional reserves. I have no citation for any of what I have said so far, as it is all based on personal observations. What I do have, is the last photo above. It is a less-cropped version of the fourth picture and I show it to demonstrate that it has consumed all of the leaves on its host plant (a Pink Periwinkle) and there is no other similar plant within reach of the larva. So, ready or not, this larva will pupate and take its chances - life or death. By capturing it and keeping it in a cage, I realize that I am interfering in nature, but I can live with that because I can feed it with all the leaves it wants, or let it pupate in the knowledge that it is truly ready to do so.