Arthropods are probably the most successful of all animals. They are found in every type of habitat and in all regions of the world. They feed on a wide variety of plant and animal materials and have been known as major causes of disease for centuries. Insects are referred to in the Bible as well as in Chinese, Greek, Roman and other historical writings. Insect-transmitted diseases have killed more soldiers than all military actions combined. Fleas, lice and mosquitoes infect humans and domesticated animals directly or indirectly with the organisms of many dangerous diseases. Arthropod stings or bites are occasionally fatal to humans. Their germ-laden saliva or contaminated bodies also are potential sources of disease transmission. Arthropods, especially insects, are vital players in the transmission of certain diseases to humans.