An unusual recruitment strategy in a mass-recruiting stingless bee, Partamona orizabaensis.

Foragers of several stingless bee species deposit attractive scent marks on solid substrates to precisely recruit nestmates to food. Interestingly, Partamona workers quickly recruit large numbers of nest mates to resources, likely even without the deposition of attractive scent marks. However, systematic studies of the recruitment system of these bees are lacking. We now studied the recruitment behavior of P. orizabaensis. Our findings show that foragers of this species can recruit large numbers of nestmates to food sources at a particular location. The precise nestmate recruitment does not rely on attractive scent marks deposited on substrates. We never observed any scent marking behavior and feeders baited with labial or mandibular gland extracts were not attractive for the bees. Chemical analyses showed that the foragers' labial gland secretions exclusively contain long chain hydrocarbons, which render their role in recruitment communication unlikely. Whether mandibular gland secretions, which contain esters and alcohols that are known as attractive pheromones in other bee species, are used to guide recruits toward food during flight, remains elusive. We conclude that Partamona's quick recruitment system that does not rely on conspicuous scent marks has evolved as a strategy against competition with sympatrically occurring and more aggressive bee species.