I response to tetrabinary's lovely post about the order Opiliones, I bring you further information about them! Specifically, the lengths the daddies in some species will go to to gaurd their babies.
Parental care in the invertebrates is somewhat uncommon. It's rare in arachnids. And care of the young by the *father* was unheard of until late in the 70's, when it was realised the harvestman Zygopachylus albomarginis
spent weeks building a little mud castle and gaurding a courtyard full of eggs and nymphs as females dropped by to examine the standard of his work and lay 4-5 more eggs. He cleans fungus off them and beats the crap out of any other males that come by, too.
A handful of other dedicated harvestmen parents, including species where the female glues her eggs to his fourth legs, and others where he'll take over if she dies, are also now known.
There was a lovely sequence about all this in Life In The Undergrowth. But I can't find it online :/ Nor can I even find a photo! :( Here's some photographs of New Zealand Harvestmen instead
Some of them have ludicrously over-large chelicerae - http://soilbugs.massey.ac.nz/gallery/IMGP6705_tif.html