Organophosphate pesticides (OPs) are derivatives of phosphoric acid with a basic structure shown in Figure 1. The majority of OPs are insecticides and have been used extensively in agriculture, commercial and residential applications since the late 1970’s, when organochlorine pesticides began to fall out of favor (Organophosphate Fact Sheet, 1996). Although the use of carbamate insecticides has grown dramatically throughout the past decade, the OPs continue to be insect control staples, with worldwide sales topping $2.9 billion in 1992 (Agrow, 1994). The organophosphates tend to be much more toxic to vertebrate populations, but are also as effective and much less expensive than the carbamate class of insecticides.