📕 Light and their colors are a powerful stimulus to attract human as well as humans. Different spectrum of light and their intensity play a major role in the physiological activity. Light stimulation change the activity of enzyme and pheromones and affect the behavior of organisms. Some key enzymes like actylcholinestrase (AChE) is triggered very fast in the exposure of red light than other one. Lymnaeidae and Planorbidae groups are of major medical and veterinary importance because they act as vector of zoonotic parasite and severely affect humans as well as cattle populations and cause heavy economic loss. Fasciolosis is a neglected tropical diseases (NTD) affects approximately fifty million people worldwide and over 180 million are at risk of infection in both developed and developing countries. Thus, a photo stimulus is a best tool for the orientation of gastropods which act as an intermediate host of many helminthic species. Present book is highlights photo and chemo attraction of fasciola larvae and their host snail.