The small size of a myrmecophyte and its associated ant colony facilitate ambushing by large Ectatomma tuberculatum workers.

Cecropia obtusa is a Neotropical myrmecophyte (i.e., plant sheltering ant colonies in hollow structures in exchange for protection against different enemies) that, in French Guiana, is associated with the dolichoderine ants Azteca alfari or A. ovaticeps that nest in this tree's internodes and are provided food, mostly food bodies called Müllerian bodies. We show that the workers of the ectatommine ant Ectatomma tuberculatum are able to select small C. obtusa individuals (i.e., they were never noted on trees more than 3 m tall) to ambush the Azteca workers exiting the entrance holes to the internodes on these trees. Their presence is more frequent diurnally when the Azteca must leave their nest to harvest Müllerian bodies, whose production requires sunlight, than at night. We witnessed 36 E. tuberculatum foragers ambushing Azteca workers, then seizing and stinging them. Exceptionally, they captured three Azteca workers successively. In all cases, they retrieved them by carrying them between their mandibles. These results confirm that E. tuberculatum foragers, which nest at the base of different tree species, are well adapted to ambushing insect prey, including social insects exiting their nests.