The long snout is, effectively, a cannon, and the guard can eject a sticky substance from it and entangle potential enemies. I had to crop this photo to exclude the distracting mess of termites that these guys were protecting.
This nymph's body is only 3 or 4mm long. Her tail is apparently composed of a waxy excretion and stretches two or three times her length.
This may be Camponotus sericeiventris, the golden carpenter ant. There are something like 900 species of ant in Costa Rica, and about 600 of them are recorded at La Selva. For the non-expert, it is very challenging to ID something like this with any level of certainty.
