Glue a small seed to the top of the 'hat' for the head. Many beetles have beautiful colors and patterns in nature. Glue two leaves of equal size to a straight stick of a length equal to or shorter than the length of the leaves. Leaf petioles can be glued on for antennae. The wings can be glued on flat or at an angle to each other.
Caterpillars Use straight or wiggly sticks.
Paint in outrageous colors.