My friend pointed out the leaves of the spider orchid before it flowered.  We placed a loop of squared fence wire around the precious flower (so the Swamp Wallaby would not eat it) and waited.  Eventually it bloomed.

Luckily I took some photographs, because I went back a few days later to find only a stalk. The flower had been cleanly severed, and was gone.  Unfortunately, without the seed head, we may not see another one next year.  As far as I can see, this was the only Spider Orchid we had this year.