I'm not sure if anyone has really seen the internal system ants use to breathe, but I thought I'd share it.
Below is an image of a Carpenter ant's tracheal system. Ants don't possess a circulatory system for oxygen and CO2, although they do have a simple blood-like haemolymph circulated by a tube-like heart for hormones and nutrients.
In order to "breathe," ants must distribute air directly to their internal tissues through tubes called trachea, which connect to a variety of air sacs and trunks that expand and contract in the ant's body. You can see the trachea branching throughout this worker's body, leading to air sacs in both the head and the abdomen. The round structures in the abdomen, by the way, are air bubbles. The oxygen and CO2 diffuse between the tissues and the trachea walls through simple osmosis.
(Image recorded in 2001 at the Advanced Photon Source, Argonne National Laboratory. Image courtesy of Wah-Keat Lee.)
All insects, including ants, rhythmically expand and contract their air sacs much like we compress and expand our lungs. In ants, it's not as visible, but in the much more physically active honeybee, the action of compressing and expanding the abdominal air sacs is obvious:
That's all folks. Hope I shared something awesome