Replicator

These strange little critters show up during thunder storms and seem to have a vicious appetite. What do they eat? Electricity! Any active power lines left unguarded will be sought out by these little pests as they attempt to suck the power out of your network. The more power going through the wire, the further away a Replicator will notice it from, and the more attracted to it they will be. If you notice one standing on top of a particularly high voltage line, you can almost guarantee that it's drawing power from it!

If they do not find 'food' within a certain amount of time, they will starve to death. Replicators drop various dusts such as redstone and glowstone dust, as well as various macerator dusts, when they die. It can be quite advantageous to put a very active line just out of their reach as a sort of trap for collection. Both to obtain its valuable drops and also to keep them away from your less protected lines.