Chemicals that kill pests by ruining their nervous system. Originally developed by the Nazis during the 1930s for use as bioweapons--"weapons of mass production," as President Bush would say. Currently the most popular class of pesticides. See Cholinesterase Inhibitors. (Chemicals from poisons and explosives, tractors from caterpillar-treaded tanks: over the years mechanized agriculture assumes more and more of the features of a war against the soil. See Agriculture. )