Constraint help on arachnid type leg's

[Scottj3d]

I am in the process of rigging these legs and would like to know how to make the joints move like a jacknife. I'm thinking I need to use a euler constraint and only allow the leg's to move on the Y axis. I've never been too good at rigging and plan to have IK off if I attempt to animate it or position it for still's. There will be a ball type swivel at the point where the leg's attatch to the thorax but that will be the only part that "swivel's". The leg joint's themselves as stated, I want to fold like a jacknife so that the part's dont "pop" out of the hinges. I've only added bones to the front leg's at this point for testing but also is there a way to copy a string of bones to add them to the other leg's?

[itsjustme]

Here's a spider rig you could tear apart for ideas.

 

To copy a set of bones, select the bone highest in the hierarchy, hold down the "Ctrl" key and drag the bone in the PWS onto the bone you want to be the parent of that set of bones. It should make a copy of the bone you dragged and all of its' children with the same names except it will add a number on the end of each name.

 

Hope that helps.