Sources : Scitalis

Lucan [1st century CE] (Pharsalia, book 9, verse 841-842): "Sole of all serpents Scytale to shed / In vernal frosts his slough..." - [Ridley, 1919

Gaius Julius Solinus [3rd century CE] (De mirabilibus mundi / Polyhistor, Chapter 27.30-31): [Chapter 27.30] The back of the scytale shines outstandingly, and the beauty of its spots gives pause to anything which beholds it. The scytale crawls rather slowly, but through its own marvel it seizes those astounded creatures which it is not otherwise able to overtake. [Chapter 27.31] Nevertheless, as bright as its scales may be, it is the first to slough its winter coat. - [Arwen Apps translation, 2011]

Isidore of Seville [7th century CE] (Etymologies, Book 12, 4:19): The scytale snake is so named because it gleams with so much variegation of its skin that it slows onlookers by the charm of its markings. And because it is rather slow at crawling, it captures those it is too slow to catch when they are mesmerized and wondering at it. It is an animal of such heat that even in the winter it sheds the skin of its heated body. Concerning it Lucan says: And only the scytale will shed its skin with frost still scattered about. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Serpents 8.34): Sytula, as Jacobus and Solinus say, is a small and malicious serpent, which kills a man with thirst. The serpent shines with such variety, that by its beauty it slows down observers, and since nature has given it a slowness in crawling, it detains those who are astonished by this miracle, whom it is otherwise unable to overtake. It is so hot that it sheds its skin in the winter. If anyone is touched by its bite, he is seized with a fiery ardor and burns. - [Badke translation/paraphrase]

Bartholomaeus Anglicus [13th century CE] (Liber de proprietatibus rerum, Book18.9): ...some be speckled, as the Serpent Scytale shineth with diversitie of speckles, that all that looketh thereon for wonder of the speckles hath lyking to looke thereon: and for he is most slow in créeping by a wonder of his diversitie of his speckles, he catcheth them yt he maye not followe in going and in créeping, and the more divers he is in coulours and speckles, the worse he is in venime, for his venime is accounted most sharpe and hot. For the same Serpent is so hot and fervent, that in winter time the skinnes that he hath chaunged, be fervent and hot, that bée of the body. Héereof Lucanus speaketh and sayth. Et Scytale sparsis etiam nunc sola pruinis. Exuujas positura suas. When frost is nigh, this Serpent changeth his skinne, as Isid[ore] saith, &c. - [Batman]