'crawler' is the ultimate Australian insult.
It was originally used to describe convicts who were on the lowest rung - ones who had no defiance left in them. The photos of the last convicts at Port Arthur that were taken at the end of the convict era and when photography was new are titled 'The Old Crawlers'.
When i was young being called a 'crawler' was fighting words - but no one really knew why - it had just survived as the ultimate insult through the generations.
Another term that has a very different meaning in Australia to the rest of the world is 'bugger' - which literally means someone who will root anything - animals, other men, etc.
In the rest of the world it is a horrible insult, but in a society that came from convicts and was originally 6 men for every woman - 'funny buggers' and 'silly buggers' are mildly disapproved of.