In this article is presented the influence upon the electroretinogram, of some external factors acting at different levels of the visual system in the fruit fly, Drosophila melanogaster. The experiments revealed the effects generated by the light intensity modification as well as by the injection of a neuropharmaceutic--the neostigmine. The increase of the light stimuli intensity induced the same change of the rate between the amplitudes of the main electroretinographic components as the neostigmine does. It was used the "flickering" excitation regime, utilizing a data acquisition system adapted to the principal experimental device.