PARTS OF INSECTS, AND MISCELLANEOUS OBJECTS. 117 



The scorpion has six visual organs, and the centipede twenty ; but other in- 

 sects, as the butterfly and dragon-fly, are gifted with a vast number of eyes, set 

 in a common ball, to which the name has been given of reticulated, or network 

 eyes. These complex organs appear to be designed for horizontal and down- 

 ward vision ; while coronet eyes are found placed upon the front and top of the 

 heads of insects. These latter organs appear as round, transparent, and shining 

 points, and are supposed to be employed for upward vision ; they are usually 

 three in number, and are generally arranged in the form of a triangle. 



RETICULATED EYES. When the eye of a butterfly or dragon-fly is viewed 

 through a powerful microscope, it resembles a piece of network, and presents 

 the appearance of a honeycomb ; each apparent cell being a perfect eye. The 

 outer surface of each is bright, polished, and round, like that of the human eye, 

 and reflects as a mirror the images of surrounding objects. What therefore is 

 commonly termed the eye of the dragon-fly, silk-worm, bee, and of other insects 

 having similar organs of sight, is in fact a complex instrument of vision, con- 

 sisting of a great number of single eyes, arranged in a globular case, each capa- 

 ble of forming distinct images of the objects before it. Dr. Hooke discovered 

 no less than 7000 single eyes in the compound eye of a horse-fly, while accord- 

 ing to the computation of Leuwenhoeck, more than 12,000 are contained in that 

 of the dragon-fly ; and M. Puget counted in each of the reticulated organs of 

 some butterflies which he examined, the astonishing number of 17,325 lenses, 

 each constituting a perfect eye. Optical artists have constructed an instrument 

 called a multiplying glass, by taking a solid piece of glass, bounded on one side 

 by a plane, and on the other by a curved surface, and then grinding and polish- 

 ing the latter into a number of flat faces, still preserving, however, the general 

 curvature. When a single object, as a flower, is beheld through this instrument, 

 its images are multiplied in proportion to the number of exposed faces, and are 

 all symmetrically arranged together, if the faces of the glass have been cut with 

 regularity. 



Reticulated eyes operate in the same manner ; and naturalists, by carefully 

 preparing these organs, and observing objects through them with the aid of a 

 microscope, have been surprised and delighted at the wonders that have met 

 their view. Not only are objects multiplied, but they are also diminished to a 

 surprising degree. As Puget gazed at a soldier through the eye of a flea, an 

 army of pigmies suddenly appeared before him, and the flame of a candle 

 flashed forth with the splendor of a thousand lamps. When Leuwenhoeck, in 

 like manner, directed his sight to the steeple of a church two hundred and 

 ninety-nine feet high, and distant seven hundred and fifty feet from the place 

 where he stood, it appeared no larger than the point of a cambric needle. 



The reticulated eyes of many flies shine with the brilliancy of the finest gems, 

 and gleam with the richest hues of light. In some the tints are red, in others 

 green, while a third class glow with a play of colors of surpassing beauty, 

 formed of mingled yellow, green and purple. Some ephemeral insects are gifted 



