The orientation inducer pheromone of the fire ant Solenopsis invicta

Foraging ants recruit nestmate workers to food sources by a variety of mechanisms. We report that one behavioural subcategory of the recruitment pheromone complex of Solenopsis invicta Buren involves orientation induction. The orientation inducer pheromone exerts its effects by changing the physiological state of the recipient rather than by releasing a measurable behaviour. Some ant species use a physical ‘waggle’ behaviour to motivate (change physiological state) nestmate workers to follow their chemical trail. The orientation inducer pheromone can be interpreted as a chemical analogue of the physical ‘waggle’ inducing effects. This behaviour is not elicited by the recruitment pheromone components responsible for orientation and/or attraction. Each of these behavioural categories is mediated by a different blend of chemicals from the Dufour's gland. Activity‐concentration thresholds indicate that the attraction and inducer part of the recruitment pheromone require about 250 times more worker equivalents for a response than the orientation pheromone. Therefore, the recruitment sub‐categories are differentially activated by the amount of Dufour's gland material released.