Here is what I came up with. I'm still going to add one more to the back before Halloween but I'm pleased with the way it turned out.
I used my embroidery machine and the embroidery design came from embroidery library. It's a great site for realistic bugs and plants. You can't tell in the photo but I changed the shape and angles of each spider to make it look more interesting and I used a shinny black embroidery thread so they really stand out. I got lots of compliments.
Embroidering on knit is challenging. I used a light weight tear away stabilizer and it didn't work well. The knit keep pulling into the feed dog. It was better after I added a second layer of stabilizer. I also had to use black thread in my bobbin because It was pulling through a bit. The last bit of advice is when you are embroidering on pre-made clothes, keep and eye on the rest of the garment so you don't sew you outfit together. This happened when we were suppose to be walking out the door. Luckily I caught it early enough and was able to save the dress.
Hope you enjoy and Happy Halloween.