In 1926, Oscar Williams of San Diego, California was granted a patent on a toy turtle operated by houseflies buzzing around inside. From patent number US1591905A, "Artificial Animal":
My invention relates to artificial animals with movable limbs and members operated by natural animals or insects and the objects of my invention are: First, to provide an animal of this class which in appearance resembles a natural animal and in which the limbs or members are movable substantially as those of the natural animal; second, to provide an animal of this class in which the limbs and members are pivotally, reliably and reciprocally mounted in the body thereof to obtain a variety of motion of said limbs and members; third, to provide an animal of this class in which the interior of the body portion or the parts containing movable members are made hollow so as to provide ample space for the movement and operation of the natural animals or insects placed within said hollow portion; fourth, to provide an animal of this class in which means are provided to keep the natural animal or insect in the interior thereof in motion and thus provide continuous movement of the said limbs or members; fifth, to provide an animal of this class with a convenient and novel means of entrance and exit of said natural animals or insects; sixth, to provide an animal of this class which is .novelly constructed and seventh, to provide an animal of this class which is very simple and economical of construction, durable, and which will not readily deteriorate or get out of order.
More at Weird Universe: Fly-Operated Turtle
