In a recent trip to western New York, I noticed a trend. Whenever I found an ant colony (flipping rocks looking for bait for a family member who likes to fish)...
an ant colony like these cornfield ants...
I found thief ants.
Take these Lasius.
Can you see the thief ants?
Let me give you clues. The thief ant is in the top right of first photo, near cluster of three larvae in second photo, and going into the tunnel just left of center in the last photograph.
Thief ants are named for their tendency to live with or near other ant colonies and then steal food from their "hosts."
They can also be found living in separate colonies.
Some of the thief ant colonies I found living by themselves were quite large.
Looks like quite a few new thief ants are on the way.
According to School of Ants, thief ants are distributed throughout the United States (although they don't show any records for New York State on the map). I had never noticed thief ants when I looked for ant colonies in that location in the past. I know my vision hasn't gotten any better, so that isn't it. It seems like thief ants have gotten a lot more numerous there.
Have you noticed more colonies of thief ants where you study ants? Do you think this a trend or a random happenstance?