Each major bamboo stalk (about 15 total)
ascends with nodes along the way where multiple branches, or shoots if
you will, splay out in all directions.

Chuck

I'm no expert but first, with the above description, it sounds like a
clumping bamboo and likely a Bambusa. Phylostachys only has two branches
from each node.

I have been told that bamboo will do poorly when the roots get too warm...
like in a dark pot in the sun. If this is the case try placing it in a
ceramic pot with a light color glaze and shade the soil with straw or
shavings or perlite to keep the soil cooler. As for dropping all its leaves,
sounds like too much water... or just stress. Add a balanced fertilizer
(slow release) wait for new shoots and cut off the old culms.

Make sure the soil drains well!!!

The ants will given enough time remove a large percentage of the soil to
make room for their nest, try to get them out..non-toxically.

Djubaya