Grease 9"x13" pan and put aside.
In a large microwave safe bowl add marshmallows and butter. Microwave on medium power for 20 seconds and stir. Repeat until completely melted.
Stir in vanilla. Add cereal 1 cup at a time and stir. Press into the pan to create the base, and smooth the top.
Pipe melted white chocolate pipe onto the back of each chocolate chip and then place 2 chips on one end of the ScAERO bar to create eyes and let set for 10 minutes.
Pipe a line of white chocolate on the bottom of the ScAERO bar and then place onto the cereal bars in a 3x4 grid - this will "glue" down the spider body
Pipe using a find tip or a sandwich page with a very small hole the milk chocolate to create 4 legs on each side of the spider.
Allow to set for 1 hour and then cut into squares so there is 1 spider per square and enjoy!