phosphorescent

hohtava, fosforoiva Having the property of emitting light for a period of time after the source of excitation is taken away, e.g., in electrostatic storage tubes and cathode-ray tubes.
1961, William S. Burroughs, The Soft Machine, page 11

So he imports this special breed of scorpions and feeds them on metal meal and the scorpions turned a phosphorescent blue color and sort of hummed.