Made a bigger, badder brother to my original Bug Bot (http://www.thingiverse.com/thing:1065468) with some design improvements to make it easier for little hands to assemble:

+Built in battery case (I will upload as a separate piece in upcoming days) --Using metal zip tie idea** from original Bug Bot, the contacts are extremely easy to make. --Jumper cable cutouts at all battery contacts for solderless connections. The battery pressing up against it gives enough resistance to hold jumpers in.
--Easy to add ON/OFF switch with 2 small screws and a small piece of metal zip tie. (OR, you can place a jumper between the two batteries for constant power.)

+Bug shaped base/body

+Larger area for vibration motor.

NOTE: I am aware that spiders have 8 legs versus 6 (hence the name "BUG Bot" and not "Spider Bot.") I experimented with 8 legs and found it to be a more difficult setup than 6 (especially for little hands.) If you want to make it more accurate, you can easily drill two more holes. Happy building and good luck!

**I don't work or sell the metal zip ties, just sharing a cool idea I had that worked better than I had expected :-)