They are prominent decomposers, especially in forests. As predators, they reduce populations of problem insects, especially caterpillars. Ladybird beetles are widely known to be important predators of aphids, and can be purchased commercially for this purpose. Detriments of beetles. A small percentage of beetles can be said to be harmful to products of humans.
Some bark beetles kill thousands of trees in western forests each year.
Agriculture in the United States is in constant threat of serious beetle pests, the prime examples being the Cotton Boll Weevil and the various species of Rootworms. Many stored foods are ruined, these including meats, dairy products, flour, meal, cereals, stored grain, nuts, and fruits. Varieties of beetles. There are approximately 100 Families of beetles in the United States. Prized by Collectors.