Insects of public health importance are described in this unit. They transmit diseases directly and indirectly from one person to another. Morphology, Life cycle, Bionomics, Public Health importance and control measures of important vectors like House fly, Louse, Ticks, Mites, Sand fly, Mosquito, Rat Flea and Cyclops are detailed. Common insecticides used are described. Chapter is concluded with additional information on medical entomology.