I hope I got the species right. This massive, 1"+ ant queen came as a real shock to me, thinking it was an ordinary worker ant. It took awhile to find out she is a queen, having just lost her wings. Look at her shoulder in #1 and you'll see where one was attached. She is a dull almost-black color with red bulbs on either side of the head.
Lowland rainforest along the north bank of the Amazon River, 60km east of Iquitos. Wikipedia says colombica is found as far south as Colombia, but I found this specimen just south of the border, so perhaps it is something else.
Check out the thumb in #4. It's a man's thumb.