Isidore of Seville [7th century CE] (Etymologies, Book 12, 5:): Eruca are leaf vermin that are wrapped up in vegetable greens or in vine-leaves; they are named from‘gnawing away’ [erodere]. This animal does not fly as the locust does, hurrying here and there and leaving half-consumed plants behind it; instead it remains on the fruit, which is doomed to die, and consumes everything with slow gliding and lazy bites. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Worms 9.10; 9.20): [Thomas describes the caterpillar under the names brucus and eruca.] [Worms 9.10] A caterpillar [brucus], as the Glossa says, is smaller in body than a cricket [adlacta], and is less able to jump. It is yellow in color. It devours vegetables, herbs, and leaves of trees with a bitter bite, and there is no remedy in the place where the multitude congregates. And in this it signifies the detractors, according to the apostle, who are hateful to God. A caterpillar does more harm than a locust, as the Experimentator says. [Worms 9.20] Eruca, as he says [i.e. Liber rerum], is a worm that has many feet. It is various in color. It eats vegetables and the leaves of trees. Around the time of September, it is said that the sky, drenched with dew or rain, suddenly changes its color and form, so those that crawl with innumerable feet can fly with wings. This worm [eruca], the locust, and the caterpillar [brucus] scourged Egypt, as read in the writings of Moses [Exodus 7-8; the ten plagues sent to Egypt do not include the caterpillar]. Also, as Isidore says, the caterpillar is a leaf worm, devouring the crops and the vegetables and the vines. It does not fly like a locust, so as to run hither and thither and leaving half eaten plants, but it continues to destroy the crops and consumes everything with a slow movement and lazy bites. And in the end the caterpillar itself is consumed after it has left in the tops of the trees something like cotton and webs, which in the following summer produce worms. And sometimes certain caterpillars enter the roofs of houses, completely changed in form, and hang on the walls in a golden color, and are there reduced to nothing. As the Experimenter says, eruca, passing through the flesh of a man, infects it, and leaves blisters behind it, and this is a sign of poison, though not of a great evil. - [Badke translation/paraphrase]

Bartholomaeus Anglicus [13th century CE] (Liber de proprietatibus rerum, Book18.46): Eruca, the Malshrag is a worme with many féet, & bréedeth in cole leaves and in vine leaves, and fretteth and gnaweth twigges, branches, fruit, and flowers, and hath that name Eruca of Erodendo, gnawing, for hée gnaweth leaves of trées and of hearbes, as Isidore sayth, libro. 12. Thereof Plautus maketh mention and sayeth, that this evill beast and wicked is enimye to the vine leafe, and wrappeth himselfe in the vine leafe and cleaveth thereto, and flieth not away hether and thether, and as a flie doth that is halfe fedde, and leaveth the leaves, but this Malshragge abideth uppon twigges and leaves, and wasteth them all with gnawing and biting, and is slow in créeping. Huc usque Isidorus li. 12. Libro. 8. Plinius sayeth, that the Malshragge is rough, as it were hairie. For in crops of trées, when hée hath gnawen the branch, and destroyed the greines therof, he weaveth certeine webs of his owne guts, as the Spinner doth, & wrappeth himselfe in those webbes, and kéepeth his shrewd Semen all the winter long. And hée layeth certeine egges, of the which commeth other broode of that kinde in springing time when trées bourgen, & by multitude of them, trees be grieved & lose their fruit, & so doth Ivie & tender hearbes. And the Malshrag is a soft worme & full of matter, distinguished with diverse coulours, shining as a Starre by night. And hath many coulours and foule shaped by day. And is not without some pestilentiall venime, for when he creepeth uppon an hotte member of a man, hee scaldeth the skinne, and maketh whelkes arise, and chaungeth his shape, as Bombax doeth that maketh silke, and this Eruca loveth the shape of a flyeng Worme, for hée taketh thin wings and broade, and flyeth up hether and thether fréely in the aire, & as many coulours as he had first in the body, so many diversities he sheweth in privie winges, and such a flieng worme is called Papilio. And Isidore sayth, libro 12. Papiliones bée called small Fowles, and bée most in fruit, as apples, and bréedeth therein Wormes that come of their stinking filth, as Isidore sayeth. For of Malshrags commeth and bréedeth Butterflyes, and of the durt of Butterflyes left uppon leaves bréedeth & commeth againe Malshrgges, & doth lesse harme in gnawing & fretting when he flyeth, then when he créepeth. And Papias sayth, that Butterflyes bée small flyeng Flyes, that come by night when lyght is kindeled in Candles, and labour to quench the lyght of the Candles, and so they be burnt in the fire of the candles, & sometime when they labor to destroy light of other beasts, they are punished and hurt in their own bodyes. - [Batman]