Green’s Dictionary of Slang

1. a girls’ school [? the girls will emerge as adult ‘butterflies’].

1909

(ref. to 1848+) in J. Ware Passing Eng. of the Victorian Era.

2. (Aus.) a drunkard [the drunkard crawls, caterpillar-like, from pub to pub or along the floor].

1941		Baker Popular Dict. Aus. Sl.
1945		Baker Aus. Lang.

3. a slow horse [its (lack of) speed].

1938

D. Runyon ‘It Comes Up Mud’ in Runyon on Broadway (1954) 532: He bets on an old caterpillar.