German cockroaches (Blattella germanica), such as the adult female with egg case shown here—are common pests in buildings throughout the world, and they can spread pathogens that cause gastrointestinal diseases as well as allergens that can cause lung reactions. Pest management professionals rely on insecticides for control of B. germanica infestations, but insecticide resistance has been reported for many populations. (Photo courtesy of Dong-Hwan Choe, Ph.D.)