I've seen this behavior in flies, but this is the first time I've seen an ant blow a bubble. The prevailing theory is that they are trying to aerate their stomach contents so beneficial bacteria can break the food down faster.
Tech Specs: Canon 1D Mark III (F13, 1/250, ISO 100) + a Canon MPE-65mm macro lens (@ 4x) with an 81A warming filter + a diffused MT-24EX.
excellent work