Preliminary quantification of freely exploring Atta insularis

Ants are social insects that typically use pheromone traces to self-organize long foraging lines without any centralized organization [1]. However, a very basic question arises: how a single ant explores new territories without any chemical or " topographical " clues? To the authors knowledge, the question is unanswered in the literature. In this paper, we offer a preliminary quantification of the free exploration of the Cuban leaf-cutter ant Atta insularis (known as bibijagua in Cuba) [5–9]. A typical experiment can be described as follows. A single individual of Atta insularis is collected from a foraging line in natural conditions, immediately taken to the laboratory, and released at the center of a 1-meter-diameter circular area made of white plastic. The trajectory of the ant is then followed by a digital camera located 1.8 meters above the center of the arena, until the ant reaches the edge of the circular platform. The illumination is provided by a 250-watt incandescent lamp located near the camera, equipped with a light diffusor, as sketched in the left panel of Fig.1. Then, the individual is released back in its natural foraging area. The experiment is replicated for several individuals collected in the same way, thoroughly cleaning the plastic arena with ethanol between repetitions. Images were averaged and the result was subtracted from each photogram, in order to distinctly visualize the moving object (i.e., the ant), on an immobile and homogeneous background. Then, images were binarized using an appropriately threshold, so the ant trajectory can be easily converted into a list of positions and times. The right panel of Fig.1 shows a typical trajectory. Figure 1. Experimental setup. Left panel: sketch of the experimental set up. The camera was a CANON EOS Rebel T3. Videos were taken at 25 frames per second, with a resolution of 4272 pixels × 2848 pixels. Right panel: Actual photogram of the experimental arena, where an experimental trajectory of a single ant is represented as a dotted line. The starting point of the trajectory is at the geometrical center of the circular arena. The first parameter we measured was the position of the ants as time goes by, which was used to