Design of choice experiments.

In each experiment, a test individual was given a simultaneous choice between two stimulus odours in a Y-olfactometer (Fig. 1). Each stimulus odour emanated from food and/or conspecifics enclosed in the two vials (1, 2) connected to the olfactometer arm. F: fresh food in vial 1+empty vial 2; NF: recently consumed food in vial 1+empty vial 2; F+C: non-feeding conspecifics in vial 1+fresh food in vial 2; FC = feeding conspecifics in vial 1+empty vial 2. Replicates: total number of tests. n: number of successful tests (tests during which the cockroach visited both olfactometer arms).