User blog comment:Mathmagician/Wall of Flesh Solo Guide/@comment-96.48.49.225-20111218222235/@comment-4674838-20111218224603

Leeches are those little red worms. I would say the most important thing is to just have a higher defense rating (36+) so that they're not an issue. Just focus on shooting The Hungry and the Wall itself and the leeches will tend to run in front of some bullets and die naturally.

If they don't, you can stop shooting the wall for a few seconds to focus fire them down. I highly recommend the Phoenix Blaster for focus firing them, rather than other weapons such as the minishark. If for some reason there's several swarming you at once, you can pull out your melee weapon and whack 'em.

Note: If your defense rating is 36, then leeches should only be doing about 26 - (36/2) = 8 damage to you per hit, which is not really a big threat.