They're actually licking sweet liquor off of a former glass bottle.

There was this stump outside of my cottage that I liked to set up bottles on so I could do some target practice with my BB pistol. One bottle had a little bit left in it, which spilled. I thought nothing of it at the time, but later when I was going out for a walk I passed the stump and just happened to glance at it. To my surprise it was covered with ants who had been considerably slowed down by the effects of the alcohol. The ants were moving so slow that I was able to compose my shots, which would normally be an impossibility.