Bryant is the author of today’s entry. He writes:
Caladenia longicauda is a tuberous perennial orchid native to Western Australia (distribution map). It flowers from July through November, and is relatively common in areas that receive significant amounts of winter moisture. The characteristic fringed labellum is the cause for its common name, the white spider orchid, making this species relatively easy to distinguish. However, there are upwards of 12 subspecies and hybrids making precise identification difficult.
The inflorescence can be single-flowered or a small panicle of several flowers, occurring at the top of a slender 15cm-60cm stem. The colourful knob-like structures on the upper surface of the labellum are termed calli. The colouration of the calli and the fringes of the labellum are thought to play a major role in the pollination process. A scent similar to the pheromones produced by receptive female thynnine wasps is produced by glands in the flowers. Male thynnine wasps are attracted by this scent, and may land on the labellum, mistaking the colourful calli for a female wasp. As the male wasp searches for its (non-existent) partner, it may contact the stigma and dislodge any pollinia it may be carrying or pick up pollinia in the process. This phenomenon is called pseudocopulation, and is common within the genus Caladenia. It not yet certain whether this is the case for Caladenia longicauda, but given the high occurrence of such sexual deception among the genus, it is thought to be likely.