BY W. R. COLLEDGE. 75 



closely set together, and bordered by white scales. In 

 certain lights they appear violet black. The anterior portion, if 

 detached, is seen to consist of colov;rless globes each absolutely 

 perfect in contour. When lit up on the microscope it is an ob- 

 ject of great beauty. There are one thousand five hundred such 

 cells in the eye. It is said that each cell is a perfect eye, con- 

 taining both a crystalline lens and also a separate branch of the 

 optic nerve. That this is really the case is proved by fig. 25, 

 which is a portion of the eye containing about one hundred and 

 fifty cells. In photographing it I used a lamp with an argand 

 burner, and each facet of the eye has reproduced the image of 

 the lamp flame, showing that every minute cell of its compound 

 eye is itself a complete optical instrument. 



The Wings 



spring from the posterior sides of the thorax, extending to the 

 last segment but one of the abdomen. They are best seen on 

 dark ground, as in fig. 26. They measure 6.8 by 1.8 mm, and 

 appear to be spotted, but that arises from tUe grouping of parti- 

 colored scales, which are mostly of a battledore form. Dividing 

 the wing into one hundred equal parts, and measuring from the 

 point of insertion into the body — 



The auxiliary vein extends to 67. 



The marginal cross one is at 15. 



The first longitudinal extends to 99. 



The second longitudinal starts at 40, begins to fork at 74, 

 the fork measuring 26 ; the lower branch, almost straight, joins 

 the apex of the wing at the centre ; the upper branch arcuates 

 slightly, the space between the two limbs being 4. 



The third longitudinal begins at 26, sloping gently to join 

 a little below the apex at 99. 



The fourth longitudinal springs from the base, forks at 7i ; 

 the upper branch, almost linear, extends to 94, the lower one, 

 89 ; the space between the branches is slightly wider than 

 the fork of No. 2 vein. 



The fifth longitudinal, springing from the axilla, is thickly 

 incrassated for the whole of its length ; curving downwards it 

 ends at 68, a thin branch shoots out at 50, joining the lower 

 border at 80. 



