Some gardeners pick beetles off by hand. You can also spray or dust your flowers with Sevin (the key ingredient is carbaryl) for Japanese beetles. If you irrigate your lawn, it's a good idea to skip irrigation in early summer and let the turf get dry to prevent the beetles from laying eggs. Japanese beetles, as you know, are green and bronze and no longer than 1/2 inch. The giant ones you describe may be some kind of weevil or another kind of beetle, and the solutions are similar.