Changes in Electrical Potential of Insect Pupae Prior to Emergence *

Using the Burr-Lane-Nims2 microvoltmeter, Burr and Hovland' have shown that there is a gradual increase in the electrical potential of chick embryos during incubation. With an instrument which differs slightly from that of Burr, and by placing the electrodes farther from the growing embryo, Romanoff and Cottrell4 obtained comparable results. In 1932 Burr formulated the theory that "the pattern or organization of any growing biological system is determined by an electrodynamic field which controls and regulates the development of every component part."' Inasmuch as chicks developing within the egg show this bioelectric pattern, it was thought of interest to determine what changes in electrical potential take place during the metamorphosis of an insect from the pupa to the adult stage. For this work a BurrLane-Nims microvoltmeter was used. In the experiment reported here 81 Samia cecropia pupae were used. In order to expose the pupae small holes were cut in the cocoons at both ends. This made it possible to apply the saline bridge electrodes directly to the anterior and posterior ends of the pupae at the time that the determinations of potential were made. Of these 81 pupae, 15 died before emergence, 33 proved to be females, and 33 to be males. To prevent drying of the exposed pupae during the time they were not being examined they were kept on moist filter-paper in large humidors. Readings were taken daily for from 3 to 94 days (average 33.8 days) before emergence.