Bugs spawn in caves and eat animals and some monsters to produes more of them. Means first they have to get up to the surface... They can destroy the block needed to get up but it would still be hard for them. BUT ONES THEY ARE ON THE SURFACE :OOO. youre dead. The only way to get rid of them and the mess they make is either running away so they despawn or using a flint and steel. I would NOT recommend fighting them as you can kill them but you will also die yourself probably...
