CHAP. III.Of theEyesandAntennæofInsects.
Of theEyesandAntennæofInsects.
To this last-mention’d Guard, we may add, that farther Guard provided in theEyesandAntennæ. The Structure of the Eye, is, in all Creatures, an admirable Piece of Mechanism; but that observable in the Eyes of Insects so peculiar, that it must needs excite our Admiration: Fenced with its own Hardness, yea, even its own accurate Vision, is a good Guard against external Injuries; and itsCornea, or outward Coat, all over beset with curious, transparent, lenticular[a]Inlets, enablingthose Creatures to see, (no doubt,) very accurately every Way, without any Interval of Time or Trouble to move the Eye towards Objects.
And as for the other Part, theAntennæ, orFeelers, whatever their Use may be in cleaning the Eyes, or other such like use; they are, in all Probability, a good Guard to the Eyes and Head, in their Walk and Flight, enabling them, by the Sense of Feeling, to discover such Annoyances, which by their Proximity may perhaps escape the Reach of the Eyes and Sight[b]. Besideswhich, they are a curious Piece of Workmanship, and in many, a very beautiful Piece of[c]Garniture to the Body.
FOOTNOTES:[a]TheCorneaof Flies, Wasps,&c.are so common an Entertainment with the Microscope, that every body knows it is a curious Piece of Lattice-work. In which this is remarkable, that everyForamenis of a lenticular Nature; so that we see Objects through them topsey-turvey, as through so many convex Glasses: Yea, they become a small Telescope, when there is a due focal Distance between them and theLensof the Microscope.This lenticular Power of theCornea, supplies, (as I imagine,) the Place of the Crystalline, if not of the vitreous Humour too, there being neither of those Humours that I could ever find, (although for Truth Sake, I confess I have not been so diligent as I might in this Enquiry;) but instead ofHumoursandTunicks, I imagine that everyLensof theCornea, hath a distinct Branch of theoptick Nerveministring to it, and rendring it as so many distinct Eyes. So that as most Animals are binocular, Spiders for the most Part octonocular, and some, (as Mr.Willughbythought,Raii Hist. Insect.p. 12.) senocular; so Flies,&c.are multocular, having as many Eyes as there are Perforations in theirCornea. By which Means, as other Creatures are oblig’d to turn their Eyes to Objects, these have some or other of their Eyes ready plac’d towards Objects, nearly all round them: Thus particularly it is in theDragon-Fly, (Libella,) the greatest Part of whose Head is possess’d by its Eyes: Which is of excellent Use to that predatious Insect, for the ready seeing and darting at small Flies all round it, on which it preys.[b]It is manifest, that Insects clean their Eyes with their Fore-legs, as well asAntennæ. And considering, that as they walk along, they are perpetually feeling, and searching before them, with theirFeelers, orAntennæ; therefore I am apt to think, that besides wiping and cleaning the Eyes, the Uses here nam’d may be admitted. For as their Eyes are immoveable, so that no Time is requir’d for the turning their Eyes to Objects; so there is no Necessity of theRetina, oroptick Nervebeing brought nigher unto, or set farther off from theCornea, (which would require Time,) as it is in other Animals: But theirCorneaandoptick Nerve, being always at one and the same Distance, are fitted only to see distantial Objects, but not such as are very nigh: Which Inconvenience theFeelersobviate, lest it should be prejudicial, in occasioning the Insect to run its Head against any Thing.And that this, rather than the wiping the Eyes, is the chief Use of theFeelers, is farther manifest from theAntennæof theFlesh-Fly, and many other Insects, which are short, and strait, and incapable of being bent unto, or extended over the Eyes: As also from others enormously long, such as those of theCapricorni, orGoat-chasers, theCadew-Fly, and divers others, both Beetles and Flies.[c]The lamellatedAntennæof some, the clavellated of others, the neatly articulated of others, the feather’d and divers other Forms of others, of theScarab,Papilionaceous Gnat, and other Kinds; are surprizingly beautiful, when view’d through a Microscope. And in some, thoseAntennædistinguish the Sexes: As in theGnat-kind, all those with Tufts, Feathers, and Brush-horns, are Males; those with short, single shaftedAntennæ, are Females.
[a]TheCorneaof Flies, Wasps,&c.are so common an Entertainment with the Microscope, that every body knows it is a curious Piece of Lattice-work. In which this is remarkable, that everyForamenis of a lenticular Nature; so that we see Objects through them topsey-turvey, as through so many convex Glasses: Yea, they become a small Telescope, when there is a due focal Distance between them and theLensof the Microscope.This lenticular Power of theCornea, supplies, (as I imagine,) the Place of the Crystalline, if not of the vitreous Humour too, there being neither of those Humours that I could ever find, (although for Truth Sake, I confess I have not been so diligent as I might in this Enquiry;) but instead ofHumoursandTunicks, I imagine that everyLensof theCornea, hath a distinct Branch of theoptick Nerveministring to it, and rendring it as so many distinct Eyes. So that as most Animals are binocular, Spiders for the most Part octonocular, and some, (as Mr.Willughbythought,Raii Hist. Insect.p. 12.) senocular; so Flies,&c.are multocular, having as many Eyes as there are Perforations in theirCornea. By which Means, as other Creatures are oblig’d to turn their Eyes to Objects, these have some or other of their Eyes ready plac’d towards Objects, nearly all round them: Thus particularly it is in theDragon-Fly, (Libella,) the greatest Part of whose Head is possess’d by its Eyes: Which is of excellent Use to that predatious Insect, for the ready seeing and darting at small Flies all round it, on which it preys.
[a]TheCorneaof Flies, Wasps,&c.are so common an Entertainment with the Microscope, that every body knows it is a curious Piece of Lattice-work. In which this is remarkable, that everyForamenis of a lenticular Nature; so that we see Objects through them topsey-turvey, as through so many convex Glasses: Yea, they become a small Telescope, when there is a due focal Distance between them and theLensof the Microscope.
This lenticular Power of theCornea, supplies, (as I imagine,) the Place of the Crystalline, if not of the vitreous Humour too, there being neither of those Humours that I could ever find, (although for Truth Sake, I confess I have not been so diligent as I might in this Enquiry;) but instead ofHumoursandTunicks, I imagine that everyLensof theCornea, hath a distinct Branch of theoptick Nerveministring to it, and rendring it as so many distinct Eyes. So that as most Animals are binocular, Spiders for the most Part octonocular, and some, (as Mr.Willughbythought,Raii Hist. Insect.p. 12.) senocular; so Flies,&c.are multocular, having as many Eyes as there are Perforations in theirCornea. By which Means, as other Creatures are oblig’d to turn their Eyes to Objects, these have some or other of their Eyes ready plac’d towards Objects, nearly all round them: Thus particularly it is in theDragon-Fly, (Libella,) the greatest Part of whose Head is possess’d by its Eyes: Which is of excellent Use to that predatious Insect, for the ready seeing and darting at small Flies all round it, on which it preys.
[b]It is manifest, that Insects clean their Eyes with their Fore-legs, as well asAntennæ. And considering, that as they walk along, they are perpetually feeling, and searching before them, with theirFeelers, orAntennæ; therefore I am apt to think, that besides wiping and cleaning the Eyes, the Uses here nam’d may be admitted. For as their Eyes are immoveable, so that no Time is requir’d for the turning their Eyes to Objects; so there is no Necessity of theRetina, oroptick Nervebeing brought nigher unto, or set farther off from theCornea, (which would require Time,) as it is in other Animals: But theirCorneaandoptick Nerve, being always at one and the same Distance, are fitted only to see distantial Objects, but not such as are very nigh: Which Inconvenience theFeelersobviate, lest it should be prejudicial, in occasioning the Insect to run its Head against any Thing.And that this, rather than the wiping the Eyes, is the chief Use of theFeelers, is farther manifest from theAntennæof theFlesh-Fly, and many other Insects, which are short, and strait, and incapable of being bent unto, or extended over the Eyes: As also from others enormously long, such as those of theCapricorni, orGoat-chasers, theCadew-Fly, and divers others, both Beetles and Flies.
[b]It is manifest, that Insects clean their Eyes with their Fore-legs, as well asAntennæ. And considering, that as they walk along, they are perpetually feeling, and searching before them, with theirFeelers, orAntennæ; therefore I am apt to think, that besides wiping and cleaning the Eyes, the Uses here nam’d may be admitted. For as their Eyes are immoveable, so that no Time is requir’d for the turning their Eyes to Objects; so there is no Necessity of theRetina, oroptick Nervebeing brought nigher unto, or set farther off from theCornea, (which would require Time,) as it is in other Animals: But theirCorneaandoptick Nerve, being always at one and the same Distance, are fitted only to see distantial Objects, but not such as are very nigh: Which Inconvenience theFeelersobviate, lest it should be prejudicial, in occasioning the Insect to run its Head against any Thing.
And that this, rather than the wiping the Eyes, is the chief Use of theFeelers, is farther manifest from theAntennæof theFlesh-Fly, and many other Insects, which are short, and strait, and incapable of being bent unto, or extended over the Eyes: As also from others enormously long, such as those of theCapricorni, orGoat-chasers, theCadew-Fly, and divers others, both Beetles and Flies.
[c]The lamellatedAntennæof some, the clavellated of others, the neatly articulated of others, the feather’d and divers other Forms of others, of theScarab,Papilionaceous Gnat, and other Kinds; are surprizingly beautiful, when view’d through a Microscope. And in some, thoseAntennædistinguish the Sexes: As in theGnat-kind, all those with Tufts, Feathers, and Brush-horns, are Males; those with short, single shaftedAntennæ, are Females.
[c]The lamellatedAntennæof some, the clavellated of others, the neatly articulated of others, the feather’d and divers other Forms of others, of theScarab,Papilionaceous Gnat, and other Kinds; are surprizingly beautiful, when view’d through a Microscope. And in some, thoseAntennædistinguish the Sexes: As in theGnat-kind, all those with Tufts, Feathers, and Brush-horns, are Males; those with short, single shaftedAntennæ, are Females.