Colour vision inDrosophila melanogaster: Wavelength discrimination

SummaryDrosophila melanogaster wildtype AS was trained to discriminate two light stimuli solely on the basis of the difference in wavelengths.1.In a choice situation between lights of different wavelength in the range from 400 nm to 600 nm the distribution of flies was measured to determine the light intensities that elicit an equal (50:50) distribution.2.A spectral sensitivity function was derived from the distribution curves (M/logI). The flies show nearly equal sensitivity in a range from 406 nm to 525 nm. For longer wavelengths the sensitivity falls off rapidly.3.At points of equal distribution conditioning experiments were carried out at 19 pairs of monochromatic lights. In general discrimination, as measured by the conditioning index, improves with increasing difference of wavelength.4.A wavelength discrimination function could thus be obtained by means of the conditioning experiments. It is characterized by two optima at 420 nm and 495 nm.