Diatomaceous earth (DE) is an excellent insect killer that is both nontoxic and long-lasting. It has long been used in the control of fleas, bed bugs, ants, and other household pests. Diatomaceous earth is a naturally occurring powder that is made from the microscopic remains of a type of algae, known as diatoms. The shells of diatoms are made out of silica, which is mined from ancient freshwater lakes and then crushed into a fine powder. This powder is soft to the touch of humans, but has microscopic razor-sharp edges that will kill insects, such as fleas.