Above:  Cecropia ants (Azteca sp.) on Cecropia.  

Like the Acacia trees we saw at Santa Rosa, the Cecropia trees recruit ants to live in them and protect the tree.  The ants drive off herbivorous insects, attack herbivorous vertebrates, and remove epiphytes and competing plants.  Their wastes also provide a lot of nitrogen to the plant.   The plant provides them with housing (inside hollow stems) and gylcogen-rich Muellerian bodies.

The photo above shows ants harvesting Muellerian  bodies from the base of the leaf petiole.  There are thickly packed hairs (trichomes) in this region, and I'm guessing the Muellerian bodies are modifications of these trichomes.

The video below shows a spider monkey (Ateles geoffroyi); included on this video are segments of a spider monkey eating cecropia ants (Azteca sp.) and another monkey carrying a baby.  Sorry it's a bit unsteady; YOU try videotaping something high up in the trees from a moving canoe! In any event, in one segment you can see the monkey plucking the palmate, umbrella-like cecropia leaves and "sucking" the ants out of the hollow stem.