Possibly Family Sphingidae “Hawk Moth” or “Sphinx Moth” ??
“The very characteristic larvae are smooth and bear a short upright horn at the end of the abdomen.”
[PICKER, M., GRIFFITHS, C. & WEAVING, A. 2004. Field Guide to Insects of South Africa. Cape Town: Struik]
Getting a field guide with photographs of every insect species with egg, larvae and adult insect identification would probably mean carrying around 5kg of information.