Meganeura likely ate other insects, lizards, and sometimes small amphibians. It was an apex predator, and was only eaten occasionally by large amphibians by the waters' edge. It is assumed that meganeuras would hunt by swooping down, snatching prey (E.G. a lizard), and flying back up to feast. They (like other dragonflies) couldn't walk, despite having more legs than us.
Mazothairos was an herbivorous flying insect that fell prey to meganeura.