Sources : Glow-worm

Pliny the Elder [1st century CE] (Natural History, Book 10, 34; 18, 66): [Book 10, 34] Glow worms shine like fires at night time owing to the color of their sides and loins, now giving a flash of light by opening their wings and now darkened by closing them; they are not much seen before the crops are ripe or after they have been cut. [Book 18, 66] And the sign alike of the barley being ripe and for sowing these crops consists in the fields in the evening shining with glow-worms (that is what the country-people call those star-like flights of insects, the Greek name for which is lampyrides) thanks to Nature's unbelievable kindness. - [Rackham translation]

Isidore of Seville [7th century CE] (Etymologies, Book 12, 8:6): The glow-worm (cicindela) is a kind of scarab, named because it gives off light when it walks or flies [from candela, “candle”]. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Worms 9.12): The cicendula is a genus of beetles, as Isidore says, and has its name from the fact that it shines when flying or walking. This is a worm in Italy; it is like a small fly. It is seen in many parts of the world, but especially in Italy. It flies a fifteen days before the summer solstice and fifteen days after the solstice. It never flies by day but only in the night, and flying like sparks it shines so brightly in the darkness, that if you saw it in the dark, you would think it an exhalation of sparks. In the tail it is particularly bright, and when it flies, more so; but when it folds his wings, it is less visible. It is endowed with a wonderful power; for if any one eats three of these worms, lust will be completely extinguished in him; and many who have tried this recommend it. Blessed, then, is he who, bright in his works and the fame of his virtues, dwells among the darkness of the world, and is not seized by darkness. - [Badke translation/paraphrase]

Bartholomaeus Anglicus [13th century CE] (Liber de proprietatibus rerum, Book18.77): Noctiluca is a litle beast, with féete and with wings, & is therefore somtime accounted among Volatiles [flying animals], & he shineth in darknes as a candle, & namely about ye hinder parts, & is foule & dark in full light, & infecteth & smiteth his hand that him toucheth: & though he be unséene in light, yet he flieth light, & hateth it, & goeth by night, and is contrary to another little one that is called Lucipeta, that riseth gladly oft light, as Isidore saith, lib. 12. cap. de minutis volatilibus &c. - [Batman]