Sometimes simple is the best way to go when it comes to freaking people out. The unseen can be more terrifying at times. Do you know someone with a fear of spiders? Just seeing these legs will probably totally freak them out. They don't even have to see the actual spider that "should" be connected to them and that is the BEST part about it!
With this prop you will create the illusion of a giant spider without having to make the complete thing, which saves on time, money & storage.

Step 1: What You Need

1 can of spray foam
Some wire pieces
Glue - that won't eat foam
Black latex paint
Piece of plywood
Putty Knife/Spatula
Thin bamboo plant supports or heavy wire
Knife - to trim pieces as necessary

Step 2: Creating the Legs

First take your piece of plywood and begin spraying lines of 3 different lengths (long, medium and short) for each segment of a leg. You can do all 8 legs or you can just do a few, it just depends on how you are going to display it. (**Note that in the pic in the Intro there are only 4 legs showing but in the final pic there are 6 legs)
Once the segments are dry, take a putty knife/spatula and sliding it between the foam and the plywood. It should come off fairly easy.
Next take a long and medium section and insert it into the center of the end of each piece. Don't glue it yet. You want to bend the segments, at the wire into the position you want. Cut off any pieces that keep them from being flush against each other.
When you have them the way you want, remove the wire and put some glue on the ends and re-insert them into the ends. If you use a hot glue gun let it cool a bit before you insert it or you may melt the foam. Now do the same with the smaller segment.
Once you have them together take a piece of bamboo, a heavy piece of wire or whatever you want to use to stake them into the ground with and glue it in the bottom end of the longest segment. (The stakes help in the painting process too. If you paint them outside, you can stake them into the ground or if you do them inside you can stake them into a bucket of sand so that you can paint them in one shot)
They are ready to paint now. I used black latex paint but feel free to make your spider legs any color you like. (Do NOT use spray paint unless you first paint the foam with a latex primer. The spray paint will eat away the foam.)