Isidore of Seville [7th century CE] (Etymologies, Book 12, 8:7): Moths [blatta] are named from their color, since indeed they stain one’s hand when they are caught, whence people also name a color ‘purple’ [blatteum]. This animal cannot bear to see light, in contrast to the fly, for the fly is light-seeking and the moth is light-fleeing, and it only goes about at night. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Worms 9.8): Moths are worms named after their color, as Isidore says, since they dye the hand when grasped; whence they are said to have a purple color [blatteum]. This worm cannot bear to see the light, and this is the opposite of the fly. For a fly seeks the light, but a moth flees the light. It is only active during the night. He who walks in the dark is ignorant and does not know where he is going. But he who walks in the day (intelligence) does not stumble, because he sees Christ, the light of this world. - [Badke translation/paraphrase]