Eryan has got it right and the great mound was like a hill and grass came to grow there again, alone in Morgoth's desert and his people wouldn't step foot upon it.
Haudh-en-Ndengin, the elves named it, the Hill of Slain, and Houdh-en-Nirnaeth, the Hill of Tears.
This was found on the last page of Chapter 20 entitled 'Of the Fifth Battle' in the Silmarillion.
While trying to find the ant using Gnampie's clue, I refound my lost
... like an old patient spider, ...
which I remembered from the BBC Radio version, and which applied to Denathor as Pippin saw him on his second day in Gondor. At 'The Battle of the Pelennor Fields' I found a "worm" and leeches. And in the Morgai were found the red eye-marked flies and also more hungry midges, while on the plains of Mordor was a town of tents that
...clustered like some huge nest of insects,...
However, I never found another ant and have grown bored with the entire project.
You may as well give the answers.