Monomorium ant's trail pheromones: Glandular source, optimal concentration, longevity and specificity

Many ants use pheromone trails to organize collective foraging. Trail pheromones are produced from different glandular sources and they may be specific to a single species or shared by a number of species. I investigated the source of trail pheromones in three Monomorium ant species: Monomorium niloticum (Emery), M. najrane (Collingwood & Agosti) and M. mayri (Forel). I also examined the optimal concentration, longevity and specificity of the pheromones. M. niloticum and M. najrane secrete trail pheromone from their venom glands, whereas M. mayri secrete trail pheromone from its Dufour's gland. The optimum concentration was 1.0 and 0.1 gaster equivalent (GE)/30 cm trail in M. niloticum, 1.0 GE in M. najrane and 5.0 GE in M. mayri. Longevity of the optimal concentration was about one day for all species. There is no species specificity among the three species of Monomorium in their trail pheromone.