1896 THE MICROSCOPE. 83 



sect which runs swiftly along and which haunts our sugar 

 stores Its body is closely covered with delicately 

 marked scales. These arc the Podura scales which were 

 so much used as test objects (fig. D). Under a medium 

 power they resemble watered silk, light and dark lines 

 wove across the scale in irregular bands. But with a 

 higher power the dark lines are seen to be rows of short 

 lines, thick at one end, very fine at the other. Yet those 

 apparent lines are not lines at all. Take a higher power 

 still and with careful mangement of the light, we shall 

 see that the apparent lines are really spaces between the 

 wedge-like particles which make up the upper-layer of 

 the scale. 



The Diamond Beetle has groups of brilliant scales 

 fashioned precisely like those of the butterfly's wings 

 but owing to their iridescence, to the peculiar thinness 

 of the upper layer and the reflecting power of the second 

 layer, the color changes like that of a soap bubble. The 

 dark cell in which the scales are set adding to their bril- 

 liancy. 



At the sea-shore may be found the Machilis (fig. G), 

 a wingless hut active little insect commonly known as 

 the Bristle Tail. Touch your finger to one of these in- 

 sects and then to a glass slide and examine under the 

 microscope. You will see myriads of the scales, some 

 heart-shaped, some shovel-shaped, some round, oval 

 elliptical, half round, half elliptical, long and narrow, 

 sometimes irregular and unequal and of various other 

 outlines, each scale has a minute footstalk which is not 

 connected with it at either extremity, but at a point of 

 one surface a little way from the smaller end, whence it 

 projects at an oblique angle, so that when the stalk is in- 

 certed in its cell the scale will lay horizontally, covering 

 the insertion (fig. G). This is a peculiarity not found in 

 many other scales. The whole body of the scale is trav- 

 ersed by five close-set parallel lines running longitudin- 



