Ant behavioral maturation is mediated by a stochastic transition between two fundamental states

Experimental set-up To investigate long-term worker behavioral maturation, we continuously recorded three queenright Camponotus fellah colonies for ~100-days. The environmental conditions and nest dimensions were identical to those described in Mersch et al (2013). Thus, colonies were housed in a double-chamber setup, with a nest box (26x16cm) that was dark 24 hours a day, connected (via a tunnel) to a foraging arena (26x16cm) under a 12:12 light-dark and temperature cycle. Underfloor reserves of water and dilute sugar solution (3g/100ml) were connected to the foraging arena via cotton wicks. Ten dead flies were also provided weekly in the foraging arena. Automated ant tracking The location of every worker within the nest and foraging boxes was determined by gluing a unique ARtag barcode to the thorax of each individual in the colony, and recording their movements using monochrome digital video cameras (4560x3048 pixels at 2 frames/sec) coupled to a machine-vision system (Fiala, 2005; Mersch et al., 2013). Physical contacts between workers were extracted based on the proximity and orientation of workers relative to one another. Worker age determination For several years prior to the experiment, and during it, newly-eclosed workers were paint-marked on a weekly basis. All worker ages given in the manuscript reflect the time elapsed since the day when the worker was painted, hence the actual age of a `5 day-old' ant is in the range 5 to 5+7=12 days old. The head, thorax and gaster of each worker was marked with a paint code indicating the week of birth. Codes were applied after immobilizing the ants by placing them in a petri dish placed on ice (dish temperature 2oC). Cooling typically lasted <5 minutes, and painted ants recovered within few minutes. Each newly-painted ant was photographed with a hand-held digital microscope (MAOZUA, 5MP USB Microscope) and comments about their physical appearance were referenced in a table. These photographs and comments were later used to distinguish between ants with the same colour code (the same age) that lost their identification tags during the same week.