I decided to dive a little deeper into the rig, see if I could try and fix the limited movement, but nothing I seemed to do was working. I don't have enough knowledge of rigging, and I couldn't find a way to fix the problem. 
I tried a number of things, such as skinning the joints to the polygon instead to see the effect it would have, but different problems arose and for some odd reason, the rig wouldn't move properly either. I couldn't move the caterpillar from the back anymore. Only the front. 
I'm not a rigger, so this is really difficult for me, and most importantly, I don't enjoy it. I wanted to challenge myself though and give it a shot. I'm glad I tried, but it really enforces the fact that rigging is most certainly not for me. 

testing the rig


With a somewhat successful rig going on here, I set up a little shot so I could do a quick test animation. 
I also had a little look online for a video of a caterpillar moving so I could sort of understand how it moves better and somehow make that movement a little more robotic. 
As I was animating, I realised there was too much space to cover as it caterpillar don't move very far, and the animation might end up taking a bit too long. So I adjusted the camera and zoomed in a bit, so it didn't have too far to travel. 
I also noticed as I was animating that the head wouldn't move much when the caterpillar's body went up, and it looked a bit strange, so I adjusted the head slightly by rotating it so it wouldn't be completely disjointed from it's body when the caterpillar moves. 
Overall, it's nothing more than a start. The rig isn't really working that great. I'd like it to have more flexibility at the back so it arches a bit better when I'm moving it. I struggle with the rigging. I find it tough to think up something suitable for it, and I don't know half the things I can do to make something move the way I want. I'm not a rigger, nor do I intend to be one. The purpose of this project was to model and texture. The rigging is something extra I decided to do as a way to push and test myself. 

This is also enforcing the point of how important a well working rig is needed for animating in maya. Doesn't matter what level of skill the animator is, if they're working with a poor rig, the results are going to be poor.