Culex (Culex) gelidus is a species of mosquito belonging to the genus Culex. It is found in India, Sri Lanka, Bangladesh, Cambodia, China, Hong Kong, India, Indonesia, Japan, Laos, Malaysia, Myanmar, Nepal, New Guinea (Island); Papua New Guinea, Pakistan, Philippines, Taiwan, Thailand, Vietnam. In 1976, it was identified as a major vector of Japanese encephalitis virus, in India. From an experiment, it was evident that aqueous solution of Calotropis gigantea leaves possess larvicidal activity, mosquito repellent activity and ovicidal activity against Culex gelidus.