Here is the updated version of Modular Formicarium. Please feel free to contact me if something is unclear. The summary below is for the original version, some parts work for both versions.

This is what I believe is the most simplest modular formicarium. It's remixed from some designs here on Thingiverse.

There are 2 modules: living and crossway There are 5 versions of living module - each with different pattern and one without pattern - plain. You can easily add any pattern you want, when you download plain living module. On the left side of living module, there is space for cotton and hole for 16mm test tube. You should make a test tube setup, but filled with water up to the top and capped of with cotton. This way, water will transfer from test tube to that space with cotton. You can cover the cotton with .stl named cotton_lid. Crossway module is used, when you want to add another row of living modules. And also, you can use it to feed your ants easily. To prevent ants from escaping, you need to print 2 feeder lids.

The air holes and humidity holes are 1.5mm in diameter. I hope ants won't escape through that. After printing, it's only 1mm for me.

Supports should only be needed for test tube connector