Caffeine is an insecticide, and I'm willing to bet it plays a role in this relationship by providing ant housing that other insects find generally unpalatable to be around.

This bit seems odd:

"This is the first ant to build its own home," says Susanne Renner, a botanist from the Ludwig Maximilian University in Munich.

Surely this is a misquote or otherwise out of context, because it's obviously not true.