Do you want to permanently mark ants in the field?
You've come to the right place.

It's fun to mark ants with fluorescent printer's ink! Ink colors can be layered, which is a great for studies that require multiple mark-recapture of the same individuals (See Kwapich and Tschinkel 2013; 2016).

     Ink can be purchased in a variety of colors from Gans Ink Inc. (http://www.gansink.com/). The inks of interest are under the fluorescent ---> visible --> oil-based inks menus. Useful colors include:  Fluorescent Orange P804 (best color), Fluorescent green P802, Fluorescent purple P807, Fluorescent yellow (P803).  The aforementioned inks do not transfer between individuals when dry *Note: The blue from Gans ink DOES NOT STICK and transfers between individual ants. Don't order the Gans blue. Instead, I use Gans Security tint base X102037 and mix it with a powder from the company Risk Reactor to make fluorescent blue (https://www.riskreactor.com/).  The powder to order from Risk Reactor is Blue Tang Fluorescent Pigment PF-14.  

      I mark ants by dissolving the ink in di-ethyl ether (10 -30% ink by volume), then spray it onto groups of ants using a 5 ml, plastic perfume sprayer (2.5 ml sprayers will not work with the solvent...trust me). This concentration and delivery method works well for Solenopsis, Pogonomyrmex and Veromessor. Ants marked as callows retain their ink marks for life: 250+ days in field nests (Kwapich and Tschinkel 2013). In contrast, the same ants are able to remove nail polish, paint pen marks, and outdoor acrylic paint overnight. The inks described above are not visible in natural light, but fluoresce under UV light.

     Marking with ink does not shorten ant lifespan, which I demonstrated by concurrently rearing groups of ants wearing wire belts(another permanent mark), belts and ink, and ink alone. Mileage may vary depending on your species. Its easy to tinker with the ink-to-ether ratio. Some UV lights are better than others for mark inspection.