Ants don't kill lawns but they do eat bug eggs. Sounds like you may have a fungal disease such as dollar spot. Take a couple of photos to your local independent garden center for a positive ID. Go to yardener.com and enter dollar spot in turf for more information. Best And Happy Yardening, Nancy.
Lawn Has Multiple Bare Spots That Appear Dead
Question From: J. Collins - ILLINOIS
Q: Hi Nancy. Our lawn in Grayslake, Il. has multiple bare spots that appear to be dead grass. When I pull up a section, I see tiny orange or red colored ants swarming. Could this be the culprit that is killing my lawn? I don't see any other insect visible. Any ideas?