They are discussed together in this fact sheet because aldrin quickly breaks down to dieldrin in the body and in the environment.
British Dictionary definitions for dieldrin
a crystalline insoluble substance, consisting of a chlorinated derivative of naphthalene: a contact insecticide the use of which is now restricted as it accumulates in the tissues of animals. Formula: C12H8OCl6
(dēl'drĭn) A light tan, toxic, carcinogenic compound used as an insecticide on fruit, soil, and seed, and in controlling tsetse flies and other carriers of tropical diseases. Chemical formula:C12H8Cl6O.