Greenhood orchids look plain but they are little marvels of nature, with the flower being an elaborate trap that forces a gnat or mosquito into a chamber where it brushes past the pistil (female bit) and anther (male bit) to pollinate it. The trapdoor is a modified petal called the labellum. To find out how they do this, I dissected a Dark-banded Greenhood orchid, and present the images above for you to see. Click to enlarge each image
These orchids lack colour, but allow light into the chamber so the insect can see where it needs to go.
Have you ever hankered to see the inside of a jug orchid? Well hanker no more. It shares the green colour and translucent chamber with the greenhood but looks so … well jug-like that I had to have a look inside. I could only bring myself to pick a mangy specimen and discovered that some rotten insect had eaten the anther.
The jug orchid also has a long trapdoor labellum and a tube that the gnat has to crawl through to escape, but the instead of hairs there is an evil looking hook that presumably pokes the gnat in the bum if it tries to reverse.
The answer is a forked counterweight and hinge in the middle to make a sensitive gate that locks into position. See below