Before they begin to spin, and about the latter end of their feeding, they must, saith the _Author_, be often changed, and have Air enough, by opening the Windows of the Room, they are in, if it be not too ill Weather; else, saith he, the Silk that is in their Belly, will cause so extraordinary a heat in them, that it burns their gutts, and sometimes bursts them; and the same (being a substance that resembleth Gum or Burgundy Pitch) will putrefy and turn into a yellowish matter. He maketh the best marks of their maturity for spinning to be, when they begin to quit their white Colour, & their green and yellow Circles, and grow of the Colour of Flesh, especially upon the tail; having a kind of _consistent_ softness shewing that they have something substantial in their Stomachs. As for their _Working_, he gives this account of it, that the first day they make only a _Webb_; the second, they form in this _Webb_ their _Cases_, and cover themselves all over with Silk; the third day, they are no longer seen, and the dayes following they thicken their _Cases_, alwayes by one _end_ or _thread_, which they {90} never break off, themselves. This, he affirms, they put out with so much quickness, and draw it so subtle and so long, that without an _Hyperbole_, the _end_ or _thread_ of every _Case_ may have two Leagues in length. He advertiseth, that they must be by no means interrupted in their work, to the end, that all the Silk, they have in their bellyes, may come out. Some eight dayes after they have finished their Work, as many of the best _Cases_, as are to serve for _seed_, _viz._ the first done the hardest, the reddest and best coloured, must be chosen, and put a-part; and all diligence is to be used to winde off the silk with as much speed, as may be, especially if the _Worms_ have nimbly dispatched their work. Here he spends a good part of his Book, in giving very particular Instructions, concerning the way of winding off the silk, setting also down the form of the Oven and Instruments necessary for that work, which is the painfullest and nicest of all the rest.