Pygidial gland chemistry and potential alarm-recruitment function in column foraging, but not solitary, Nearctic Messor harvesting ants (Hymenoptera: Formicidae: Myrmicinae)

- Column foraging Nearctic Messor have large pygidial gland reservoirs.
- Pygidial gland secretions act as air-borne alarm-recruitment pheromones.
- n-Tridecane, found in pygidial gland reservoirs, elicits alarm-recruitment.
- Solitary foraging congeners lack large pygidial gland reservoirs.
- Two column foraging Palearctic Messor do not have pygidial gland reservoirs.