The DDT Successor is DEET, a four-letter acronym for N, N-Diethyl-meta-toluamide. DEET is an insect repellent that has been used since the 1940s to protect against mosquitoes, ticks, fleas, and other biting insects. It is one of the most widely used insect repellents in the world and is considered safe when used as directed. DEET is often used in combination with other insect repellents, such as permethrin, to provide additional protection against biting insects.