Insects are considered pests for a variety of reasons, including direct damage by feeding on crop plants in the field or by infesting stored products, indirect damage by spreading viral diseases of crop plants (especially by sucking insects such as leafhoppers), spreading disease among humans and livestock, and annoyance to humans. Examples of insects regarded as pests include the phylloxera, migratory locusts, the Colorado potato beetle, the boll weevil, Japanese beetle, aphids, mosquitoes, cockroaches, the Western corn rootworm, and some fly species.