Line a baking sheet or large tray with parchment paper.
Melt chocolate in microwave according to package instructions. One at a time, dip each marshmallow in chocolate until coated. Place marshmallows on prepared baking sheet and sprinkle tops with orange sugar.
Place marshmallows in refrigerator for at least 1 hour, or until chocolate shell is completely set and hard.
Once chocolate coating is set, remove one marshmallow from the baking sheet. Using the white icing as glue, stick 4 pretzel halves on each side of the bottom of the marshmallow. These are the spider’s legs.
Put two dots of white icing on the top of the marshmallow. Place a miniature chocolate chip on each white dot to make the spider’s eyes.
Repeat process for each of the remaining 11 marshmallows. Return marshmallows to refrigerator to allow white icing to set. Keep cold until ready to serve.