Micrographia - or some physiological descriptions of minute bodies made by magnifying glasses with observations and inquiries thereupon/Chapter 41
Observ. XLI. Of the Eggs of Silk-worms, and other Insects.
THe Eggs of Silk-worms (one of which I have describ'd in the second Figure of 25. Scheme) afford a pretty Object for a Microscope that magnifies very much, especially if it be bright weather, and the light of a window be cast or collected on it by a deep Convex-glass, or Water-ball. For then the whole surface of the Shell may be perceiv'd all cover'd over with exceeding small pits or cavities with interposed edges, almost in the manner of the surface of a Poppy-seed, but that these holes are not an hundredth part scarce of their bigness; the Shell, when the young ones were hatch'd (which I found an easie thing to do, if the Eggs were kept in a warm place) appear'd no thicker in proportion to its bulk, then that of an Hen's or Goos's Egg is to its bulk, and all the Shell appear'd very white (which seem'd to proceed from its transparency) whence all those pittings did almost vanish, so that they could not, without much difficulty, be discern'd, the inside of the Shell seem'd to be lin'd also with a kind of thin film, not unlike (keeping the proportion to its Shell) that with which the shell of an Hen-egg is lin'd; and the shell it self seem'd like common Egg-shells; very brittle, and crack'd. In divers other of these Eggs I could plainly enough, through the shell, perceive the small Insect lie coyled round the edges of the shell. The shape of the Egg it self, the Figure pretty well represents (though by default of the Graver it does not appear so rounded, and lying above the Paper, as it were, as it ought to do) that is, it was for the most part pretty oval end-ways, somewhat like an Egg, but the other way it was a little flatted on two opposite sides. Divers of these Eggs, as is common to most others, I found to be barren, or addle, for they never afforded any young ones. And those I usually found much whiter then the other that were prolifick. The Eggs of other kinds of Oviparous Insects I have found to be perfectly round every way, like so many Globules, of this sort I have observ'd some sorts of Spiders Eggs; and chancing the last Summer to inclose a very large and curiously painted Butterfly in a Box, intending to examine its gaudery with my Microscope, I found within a day or two after I inclos'd her, almost all the inner surface of the Box cover'd over with an infinite of exactly round Eggs, which were stuck very fast to the sides of it, and in so exactly regular and close an order, that made me call to mind my Hypothesis, which I had formerly thought on for the making out of all the regular Figures of Salt, which I have elsewhere hinted; for here I found all of them rang'd into a most exact triagonal order, much after the manner as the Hemispheres are place on the eye of a Fly; all which Eggs I found after a little time to be hatch'd, and out of them to come a multitude of small Worms, very much resembling young Silk-worms, leaving all their thin hollow shells behind them, sticking on the Box in their triagonal posture; these I found with the Microscope to have much such a substance as the Silk-worms Eggs, but could not perceive them pitted. And indeed, there is as great a variety in the shape of the Eggs of Oviparous Insects as among those of Birds.
Of these Eggs, a large and lusty Fly will at one time lay neer four or five hundred, so that the increase of these kind of Insects must needs be very prodigious, were they not prey'd on by multitudes of Birds, and destroy'd by Frosts and Rains; and hence 'tis those hotter Climates between the Tropicks are infested with such multitudes of Locusts, and such other Vermine.