Insecticides kill insects, wasps, hornets and bees and prevent their destructive behavior. They are commonly sprayed in and around facilities on plants, wood, and siding. Stomach insecticides are delivered through traps and are effective on insects that chew, such as ants or caterpillars. Contact insecticides are sprayed directly on insects and absorbed through the body’s wall. They are effective on soft-bodied insects. Fumigants are inhaled by insects and are ideal for insects out of reach of sprays, such as roaches, bedbugs and beetles.