Scorpions emit fluorescence…when they are illuminated with ultraviolet light. It is supposed to be a kind of warning. The same happens with centipedes. In biology this phenomenon is called aposematism, that is, warning mechanisms to indicate that they are dangerous.
There are several types of aposematism, especially in relation to color (intense colors such as red, yellow, blue, black …), but also in relation to sound and chemicals.