Invidia rumpuntur aves neque noctua curat.
The birds burst with envy, and the owl doesn't care.
Notice how there are no breaks between the words. That made reading much more difficult, and people would usually read aloud in order to "hear" where the word breaks were. Having breaks between the words helped to make silent reading more practical.
There are some other gorgeous mosaics at the museum in El-Djem; you can read more about that here: Thysdrus (El Djem): the Museum. I really like this one of a sea nymph riding on a sort of hybrid sea-horse with a sea-serpent's tail and wings!