# Micrographia/Chapter 42

Observ. XLII. Of a blue Fly.
This kind of Fly, whereof a Microscopical Picture is delineated in the first Figure of the 26. Scheme, is a very beautifull creature, and has many things about it very notable; divers of which I have already partly describ'd, namely, the feet, wings, eyes, and head, in the preceding Observations.
And though the head before describ'd be that of a grey Drone-Fly, yet for the main it is very agreeable to this. The things wherein they differ most, will be easily enough found by the following particulars:
First, the clusters of eyes of this Fly, are very much smaller then those of the Dron-Fly, in proportion to the head.
​ Schem. XXVI. ​And next, all the eyes of each cluster seem'd much of the same bigness one with another, not differing as the other, but rang'd in the same triagonal order.
Thirdly, between these two clusters, there was a scaly prominent front B, which was arm'd and adorn'd with large tapering sharp black brisles, which growing out in rows on either side, were so bent toward each other neer the top, as to make a kind of arched arbour of Brisles, which almost cover'd the former front.
Fourthly, at the end of this Arch, about the middle of the face, on a prominent part C, grew two small oblong bodies, D D, which through a Microscope look'd not unlike the Pendants in Lillies, these seem'd to be jointed on to two small parts at C, each of which seem'd again jointed into the front.
Fifthly, out of the upper part and outsides of these horns (as I may call them, from the Figure they are of, in the 24. Scheme, where they are marked with F F) there grows a single feather, or brushy Brisle, E E, somewhat of the same kind with the tufts of a Gnat, which I have before described.
What the use of these kind of horned and tufted bodies should be, I cannot well imagine, unless they serve for smelling or hearing, though how they are adapted for either, it seems very difficult to describe: they are in almost every several kind of Flies of so various a shape; though certainly they are some very essential part of the head, and have some very notable office assign'd them by Nature, since in all Insects they are to be found in one or other form.
Sixthly, at the under part of the face F F, were several of the former sort of bended Brisles, and below all, the mouth, out of the middle of which, grew the proboscis G H I, which, by means of several joints, whereof it seem'd to consist, the Fly was able to move to and fro, and thrust it in and out as it pleas'd; the end of this hollow body (which was all over cover'd with small short hairs or brisles) was, as 'twere, bent at H, and the outer or formost side of the bended part H I, slit, as it were, into two chaps, H I, H I, all the outside of which where cover'd with hairs, and pretty large brisles; these he could, like two chaps, very readily open and shut, and when he seem'd to suck any thing from the surface of a body, he would spread abroad those chaps, and apply the hollow part of them very close to it.
From either side of the Proboscis, within the mouth, grew two other small horns, or fingers, K K, which were hairy, but small in this Figure; but of another shape, and bigger in proportion, in the 24. Scheme, where they are marked with G G, which two indeed seem'd a kind of smellers, but whether so or not, I cannot positively determine.
The Thorax or middle part of this Fly, was cas'd, both above and beneath, with a very firm crust of armour, the upper part more round, and covered over with long conical brisles, all whose ends pointed backwards; out of the hinder and under part of this grew out in a cluster six leggs, three of which are apparent in the Figure, the other three were hid by the ​body plac'd in that posture. The leggs were all much of the same make, being all of them cover'd with a strong hairy scale or shel, just like the legs of a Crabb or Lobster, and the contrivance of the joints seem'd much the same, each legg seem'd made up of eight parts, 1, 2, 3, 4, 5, 6, 7, 8, to the eighth or last of which, grew the soles and claws, described before in the 38. Observation.
Out of the upper part of this trunck grew the two wings, which I mention'd in the 38. Observation, consisting of a film, extended on certain small stiff wires or bones: these in a blue Fly, were much longer then the body, but in other kind of Flies they are of very differing proportions to the body. These films, in many Flies, were so thin, that, like several other plated bodies (mention'd in the ninth Observation) they afforded all varieties of fantastical or transient colours (the reason of which I have here endeavoured to explain) they seem'd to receive their nourishment from the stalks or wires, which seem'd to be hollow, and neer the upper part of the wing L L several of them seem'd jointed, the shape of which will sufficiently 'appear by the black lines in the second Figure of the 26. Scheme, which is a delineation of one of those wings expanded directly to the eyes.
All the hinder part of its body is cover'd with a most curious blue shining armour, looking exactly like a polish'd piece of steel brought to that blue colour by annealing, all which armour is very thick bestuck with abundance of tapering brisles, such as grow on its back, as is visible enough by the Figure.
Nor was the inside of this creature less beautifull then its outside, for cutting off a part of the belly, and then viewing it, to see if I could discover any Vessels, such as are to be found in a greater Animals, and even in Snails exceeding manifestly, I found, much beyond my expectation, that there were abundance of branchings of Milk-white vessels, no less curious then the branchings of veins and arteries in bigger terrestrial Animals, in one of which, I found two notable branches, joining their two main stocks, as it were, into one common ductus; now, to what veins or arteries these Vessells were analogus, whether to the vena porta, or the meseraick vessells, or the like, or indeed, whether they were veins and arteries, or vasa lactea, properly so called, I am not hitherto able to determine, having not yet made sufficient enquiry; but in all particulars, there seems not to be any thing less of curious contrivance in these Insects, then in those larger terrestrial Animals, for I had never seen any more curious branchings of Vessels, then those I observ'd in two or three of these Flies thus opened.
It is a creature active and nimble, so as there are very few creatures like it, whether bigger or smaller, in so much, that it will scape and avoid a small body, though coming on it exceeding swiftly, and if it sees any thing approaching it, which it fears, it presently squats down, as it were, that it may be the more ready for its rise.
Nor is it less hardy in the Winter, then active in the Summer, induring all the Frosts, and surviving till the next Summer, notwithstanding the ​bitter cold of our Climate; nay, this creature will indure to be frozen, and yet not be destroy'd, for I have taken one of them out of the Snow whereon it has been frozen almost white, with the Ice about it, and yet by thawing it gently by the warmth of a fire, it has quickly reviv'd and flown about.
This kind of Fly seems by the steams or taste of fermenting and putrifying meat (which it often kisses, as 'twere, with its proboscis as it trips over it) to be stimulated or excited to eject its Eggs or Seed on it, perhaps, from the same reason as Dogs, Cats, and many other brute creatures are excited to their particular lusts, by the smell of their females, when by Nature prepared for generation; the males seeming by those kind of smells, or other incitations, to be as much necessitated thereto, as Aqua Regis strongly impregnated with a solution of Gold, is forced to precipitate it by the affusion of spirit of Urine, or a solution of Salt of Tartar.
One of these put in spirit of Wine, was very quickly seemingly kill'd, and both its eys and mouth began to look very red, but upon the taking of it out, and suffering it to lie three or four hours, and heating it with the Sun beams cast through a Burning-glass, it again reviv'd, seeming, as it were, to have been all the intermediate time, but dead drunk, and after certain hours to grow fresh again and sober.