I googled what eggs look like, and those seemed to be eggs! I wonder where they were moving I mean, the guys were moving out... everything's fine, but the nasty neighbor (me) blocked their hole... what a bad person LOL
Anyway, we are enjoying outdoors again. The slit is tightly plugged by paper towel for now and I don't see any ants. I thought why can't I tape it with post tape instead of caulk?

Taping it is fine, but it won't be as permanent as caulk so you might have to put up new tape occasionally.