Pyrethrins (this chemical compound) act on insects by paralysing their nervous systems. Pyrethrins are among the most widely used insecticides because they have low toxicity to humans and other animals. Pyrethrins are extracted from chrysanthemum flowers. This chemical compound has been used since ancient times for killing pests on crops and other plants. Pyrethrins have been used since 1920s in agriculture for pest control. It was first synthesised by Robert Higgins and Frederick Joliffe at Rutgers University in New Jersey in 1920. This chemical compound was first used commercially by FMC Corporation in 1939 for control of caterpillars on potatoes and cucumbers. Zidua contains 1% pyrethrins and 96% propane-1,2-diol (1:1 mixture). Propane-1,2-diol has been added as an adjuvant because it acts as a preservative in insecticides.