I spent this afternoon at my outlaw's home and had quite the treat awaiting me. I was walking around the clearing where I found my Formica pallidefulva queen when I noticed an audible scratching sound in the leaves. Upon further inspection, I saw what was the beginning of a column of 'red ants'. The column was creeping through the scrub brush with the vanguard sweeping left to right, guiding the column along what I can only imagine was a trail to their target.
There were so many of these ants I could hear them from about 10 feet away. At first, their appearance alone captivated me. They were a brilliant red, with an almost golden or orange glow from the reflection of the sun on their gasters. Their size itself was not remarkable. For the most part, they were all just slightly larger than the local Formica glacialis workers. Of course, there were slight variations amongst them.
Anyhow, I watched them wind their way through the forest. They ended up traveling approximately 30 meters from their nest (which I was unable to see as it was beneath the leaves and I had no intentions of disturbing their movement). At first, I thought they had lost their trail as they had started to gather around some tufts of grass. Their behavior went from methodical to an almost frenzied state. The center of the mass was busy ripping at the base of the grass stalks while the outer ring was occupied with scouting the perimeter. This was when I spotted a few Formica workers approaching with caution. Unfortunately, I was so taken with the raiders that I have since forgotten the physical description of the defending ants. They were noticably smaller than the invaders. If I had to make an educated guess, I'd say they were a dull red/brown mix with darker gasters.
Eventually, the raiders broke through the sealed entrances and emerged with their prize. They were done within 15 minutes of gaining entry to the colony. I did manage to grab one worker to inspect her. I wasn't aware Polyergus was native to this portion of Michigan, but she certainly had some nasty sickle mandibles. Comparing pictures, I would venture to say that they were Polyergus breviceps. This was by far, the most thrilling thing in the ant world I have had the privilege to watch. They raided the host nest with such efficiency! It makes me wonder how they don't eliminate all of their host species in the area. The Formica were outmatched completely. When slavers raid, do they destroy the host colony or do they just take their young?
I only wish I had my video camera with me!