You will need:
1 boxed cake mix
eggs (depends on your mix)
2 Cups chocolate frosting
1 Cup accent color frosting
8 long thin black licorice ropes
Bake cake according to directions. I used a glass pampered chef 8-cup measuring bowl for the cake body. A bundt pan would also be cute for the spider.
When finished baking, run a knife between the pan and the cake to loosen the sides. Let cake cool in pan for 15 minutes. Remove carefully from the pan and place on a plate or platter. Cover with plastic wrap and freeze. Freezing the cake eases the frosting process. You don't end up with crumbs breaking off with the frosting.
Remove frozen cake and put a thin layer of frosting on cake.
Next use a cake decorating tip with a manual cake decorating bag or pump. I used the 8 pronged tip for the furry spider effect and cover your cake. I accented the cake with the pink frosting (it needed to be a little girly) Make small holes in cake (Your cake will probably still be mostly frozen) where you want your spider legs and place licorice ends in top of cake. A chopstick end makes perfect sized holes for skinny licorice legs. Drape down to plate. Use skittles for eyes and border spider with candy corns. We also used the candy corns as spider feet.
Have Fun. I am positive you can improve on this decorating, absolutely positive.