Bacillus thuingeinsis is a facultative anaerobe. It is a motile and spore forming, gram-positive bacteria found in the soils, water and on leaf surface. Bacillus thuringiensis var israelensis (Bti) produce cry toxins which acts as a larvicides. Cry toxins are activated by the midgut alkaline pH of mosquito larvae and damage the midgut epithelial cells. These crystal proteins are protoxins, these protoxins are converted to toxins and the bodies are solubilized. Pyriproxyfen greatly effects the insect growth and development. These substances are called as “insect hormone mimics” or “insects growth regulators” (IGR’s) that effects on the physiological regulatory processes (necessary for the normal development of insects or their generation or progeny). This book demonstrates that how Bti and IGR act on the Aedes larvae and consequently decreases the growth and normal development.