Figure 5.

Orchid bees use brightness cues to determine the size of an aperture. (a) The percentage choice of aperture when presented with a triangle (60 mm wide, 90 mm high) and a 60 mm diameter circle or with two circles, 43.4 mm and 60 mm in diameter. Black bars indicate the percentage of bees that flew through the aperture with the smallest greatest clearance to the edges; white bars represent the percentage of bees that flew through the 60 mm diameter aperture. (b) The aperture choice when bees were presented with the 43.4 mm and 60 mm diameter apertures that were either illuminated with lights of the same intensity (left bars) or when the intensity of the light behind the larger aperture was dimmed (right bars). Numbers indicate the number of individuals that flew through each aperture.