This is a great project for the month of October. My kids really enjoyed this and I am sure your's will to.
First you need to trace the bottom of the circle pie tray onto the black construction paper and cut out the circles.
Lay down newspaper so paint does not get on the table. Put white paint into a meat tray and roll about 4-5 marbles in the paint. Put the black circle in the pie tray and then put one of the marbles that has been dipped in paint into the pie tray. The child will then move the pan around and it will look like a spider web. You may need to take the marble out and put in a new one with more paint.