Green’s Dictionary of Slang

rock spider n.

[in Aus. senses, in nursery rhyme ‘Little Miss Muffet’: ‘There came a big spider / And sat down beside her’]

1. [1930s+] (Aus., also spider) a thief who robs courting couples in parks or at the seaside when their attention is elsewhere.

2. [1950s+] (S.Afr.) an Afrikaner.

3. [1990s+] (Aus., also spider) a sexual offender, usu. a paedophile or child molester.