Don't let the intricacy of these ants, centipedes, beetles and spiders deter you from trying your hand at this creepy design. All you need is an insect guide from your local library for reference. Besides, the shapes needn't be exact, just suggestive -- your mind will fill in the rest.
To make these critters look three-dimensional, you'll want to paint them on in layers. Begin by mixing orange, blue and red face paint to create a beige shade that's just a little darker or lighter than your child's complexion. Then use the mixed hue to paint a shadow for each bug. (Note: The shadows should be a little bigger than the insects you plan to paint on top of them.) For an extra-creepy effect, you can even add bug bite marks near a couple of the shadows -- mix together white and red face paint and use a fingertip to dab it onto your child's skin.
Now use green, orange, red, blue and black face paint to paint the bugs on top of their shadows. A narrow margin of the beige undercoat should remain visible along the edges.
Top each bug with a dab of white face paint. This will make the bugs look like they have shiny shells.
For a finishing "cobweb" effect, you can spray your child's hair with temporary silver hair color and then bobby-pin on assorted plastic bugs. (Both the hair spray and the bugs are available at many pharmacies and novelty stores.)