Split thorn of a bullshorn acacia, revealing a nest of its ant mutualists.

Janzen's detailed natural history of the interaction between bullshorn acacia and ants suggests interactions of mutual benefit to both partners (fig. 15.6). Newly mated Pseudomyrmex queens move through the vegetation searching for unoccupied seedlings or shoots of bullshorn acacia. When a queen finds an unoccupied acacia, she excavates an entrance in one of the green thorns or uses one carved previously by another ant. The queen then lays her first eggs in the thorn and begins to forage on her newly acquired home plant. She gets nectar for herself and her developing larvae from the foliar nectaries and gets additional solid food from the Beltian bodies. Over time, the number of workers in the new colony increases, and the queen shifts to a mainly reproductive function.