Fig. 1. A top-down schematic of video-camera placement. The cameras were on tripods, set to the same height, and oriented horizontally, as determined by a level. Cameras were at right angles to one another, and both 1 m from the entrance of an identified nest, positioned at the center of each frame. Each camera had its own infrared (IR) light source, and an external array of IR light-emitting diodes lit the area from below; these lights are invisible to humans and bees.