Possible Duplicate:
How can I mitigate the damage I get from the poisonous flying insects in Caldeum
What can I do to increase the defense against those damn wasps in the desert of Act 2? I can have a bunch of enemies slashing me and my health barely goes down, but once the wasps start hitting me, it drains my health faster than anything in the game.
The damage from the little bugs that the wasps put out is poison damage. You can increase your resistance to that either through intelligence stacking or straight up +poison resistance gear.
Another way of mitigating the effect is simply to stack a little more vitality to absorb the health impact. Those bugs can make quick work of anyone with a low health pool (as my monk found out very early on).
However, the best way to go is probably just to make them priority targets. Melee will have a tough time running them down without some teleporting abilities, but ranged DPS can make quick work of them, as they have fairly low HP.
Best advice is to dodge. Their projectile speed isn't that slow for no reason and since it's avoidable (even though it can get annoying dodging their attacks and chasing after them) they made it a harder hitting attack than others that are not that easily avoidable (like the Dark Berserker in Act I with their smash attack).
