Structure of Insects' Wings. 31 



bends which it then takes ; and at d, how tidily it is 

 packed ready to lay along the insect's back ! But let 

 us pause before we hurry it thus out of sight, and 

 turn again to its pictured representation, fig. 2, as 

 shown through a small magnifying-glass. The wing 

 should be held somewhat obliquely to the light, and 

 then the lovely colours, green, blue, red, and golden, 

 gleam with a soft radiance. 



Do you ask the reason why we examine this wing 

 simply with a magnifying-glass, instead of with the 

 large microscope? It is because, taking the entire 

 wing, it is rather too large an object to be shown at 

 once. The lowest power of my microscope is twenty 

 diameters, and this object, you see, measures three- 

 eighths of an inch in width, so that if magnified to 

 twenty times that diameter, it would be shown a length 

 of seven inches and a-half, and, turn it as you might, 

 could not be fitted into a page of this book. And 

 here, perhaps, the question may arise, " Is fig. 2 only 

 four times larger than fig. 1, a t" The answer is, it 

 is four times its diameter, and this is the measure 

 employed in works on the microscope, and called the 

 " linear measure." It signifies that the object, when 

 stated to be, as in the present instance, ( ' magnified 

 four diameters," appears four times the height and 

 four times the breadth that the unassisted eye observes 

 it. The representation of the wing at fig. 2, takes up 

 sixteen times the space occupied by fig. 1, a; and 

 that statement of the amount to which it is magnified 

 is called the " superficial measure," or measure of the 

 surface, and can always be calculated by squaring the 



