Calculation of visual receptor spacing inDrosophila melanogaster by pattern recognition experiments

Abstract

1. Drosophila flies show a very pronounced tendency to move towards vertical black stripes when confronted with both vertically and horizontally striped patterns. 2. Within the range 4.8°<λ<9.5° of pattern wavelengths horizontal stripes are preferred. No pattern preferences are found at the zero-points λ01=9.5° and λ02 = 4.8°. For a constant pattern wavelength these zero-points are not affected by the ratio of the widths of black and white stripes. Therefore, the sign of the reaction frequency to vertical black stripes depends on the pattern wavelength and not on the width of the black stripes. 3. The vertical stripe preference is discussed to be a mechanism of loeomotor course control. Thus referring to movement perception concepts a receptor spacing of Δϕ=4.8° can be deduced from the pattern recognition tests. 4. Receptor spacing ofTenebrio molitor beetles is calculated for comparison (λ01=19°). 5. No pattern preferences are found inDrosophila melanogaster, when the vertical and horizontal stripes are offered on ground glass screens (u.v. free and u.v. containing light), being the only light sources within the whole apparatus. In that situation the flies show a mere phototactic behavior.