The Eltham copper butterfly and the Notoncus ant are BFFs for life. The ants lovingly raise the butterflies' caterpillar babies, while feasting on the sweet substance the caterpillars produce. Everybody wins in this prime example of mutualism.
The pseudoscorpian is a total freeloader. When it wants to get around, it boards the back of the giant harlequin beetle, in a one-sided setup called commensalism.
Parasitism is where things get...