Some adders occasionally turn black. This isn`t a fault when born it is actually a stage of evolution (as scientists recon) as they are cold blooded and black exorbs heat. Scientists recon that in 10 years most adders will be becoming black as the climate becomes colder and the need to warm up becomes more valuable. Black adders can vary from being completely black or being able to see the zigzag. Black adders are pretty rare at the moment.