It was the caterpillar of Hong Kong's largest and most spectacular moth, and caterpillar, Attacus atlas, or the Atlas moth, seen here photographed in late May 2021.
I am lucky enough to live near two different locations where I can find them quite regularly, and I have enjoyed taking some people to see them, and watch them grow.
Even after hatching, see junior below, Atlas moths begin their lives as good-sized caterpillars. They feed ravenously on their favourite leaves from citrus, guava, and cinnamon plants. They do this as the adult moth does not eat, so the caterpillar takes in enough food to last for their pupa and adult moth stages.
Here is an iPhone shot of one near my hand...I told you, they are huge!
The caterpillars can reach up to four and a half inches in length before they pupate.
Here is a young one, much smaller, still quite distinctive, but also different in appearance.
And some more pictures of the adult, with this one so large I think he will pupate soon. This one is interesting also as he appears to have blue legs.
more food....and it does remind me of the The Very Hungry Caterpillar book. Did you know that it is frequently cited as one of the best picture books of all time. The author, Carle, gave his view on the book:
"I remember that as a child, I always felt I would never grow up and be big and articulate and intelligent. ‘Caterpillar’ is a book of hope: you, too, can grow up and grow wings".
They have a threatening appearance, and also a secretion that has a powerful odour and can be used against predators like ants and lizards