The rig i belive is fine, but i think I see your problem. The tips of the legs dont have the fangs skinned to them, did you properly weight paint this? If you didnt delete all the vertex groups and weight paint, and if you did weight paint, still delete all the vertex groups and re paint. Also all your IK TARGET bones should have the deform turned off. I suggest parenting them to the body bone and make them perpendicular to the legs so you can see them easier. Each leg should be a complete chain of bones btw. For the eyes, parent them to the body bone and make a new bone in front of the body bone, and add a track to constraint to the eyes targeting the new bone, that way the eyes will follow that bone.
Hopefully i was clear, but if you have any questions…post away
BTW, no lattice is needed, latices are for deformations
One more thing, rig in rest pose, not some funky rotated one
Oh and please name your bones!
And speaking of naming, your spider is symmetrical so make the rig symmetrical, so you do half the work! (name the right side with a .R in the end then after applying all the IK ans stuff, select the right side SHIFT-D, S, X, -1 with the cursor in the center of the spider and pivot point set to the cursor.
Wow, lol, every second i look at it i find more stuff to comment about…Your bone rolls are all messed up…