About this photo:

Note that this is a true spider, not a "Daddy Longlegs." Those are technically a different Order of the Class Arachnidae. Harvestmen, or Daddy Longlegs, have a single body part, not two, and don't make webs or have venom. This family of spiders is sometimes called "Daddy Longleg Spiders." I have several shots of these interesting spiders. They have remarkably thin and flexible legs which appear almost transparent in some light conditions. Here the body also appears to be partly transparent.

There are many of these spiders in the Hornsby Bend greenhouse, mainly on the walls, where they create messy webs around poles and other obstructions.