Vector transmission of pathogens affecting human, animal, and plant health continues to plague mankind both in industrialized and Third World coun­ tries. The diseases caused by these pathogens cost billions of dollars an­ nually in medical expenses and lost productivity. Some cause widespread of food-and fiber-producing plants and animals, whereas others destruction present direct and immediate threats to human life and further development in Third World countries. During the past 15 years or so, we have witnessed an explosive increase in interest in how vectors acquire, carry, and subsequently inoculate dis­ ease agents to human, animal, and plant hosts. This interest transcends the boundaries of anyone discipline and involves researchers from such varied fields as human and veterinary medicine, entomology, plant pa­ thology, virology, physiology, microbiology, parasitology, biochemistry, molecular biology, genetic engineering, ultrastructure, biophysics, bio­ systematics, biogeography, ecology, behavioral sciences, and others. Ac­ companying and perhaps generating this renewed interest is the realization that fundamental knowledge of pathogen-vector-host interrelationships is a first and necessary step in our quest for efficient, safe methods of disease control.