86 



EVENINGS AT THE MICROSCOPE. 



SCALE OF Br.ISTLF.-TAlL. 



willi it at either extremitj, but at a point of one surface 

 a little ^vaJ from the smaller end, ■v\-lience it projects at 

 an oblique angle ; so that Avhen the stalk was inserted 

 in its proper cell in the skin of the insect, the scale lay 



horizontallr, covering the insertion. 

 This is a peculiarity not found in 

 some other scales that I shall pres- 

 ently introduce to yon. 



The whole body of the scale is 

 id-^:rrjrHadd:^H|;( traversed by a series of fine close-set 

 v^-i-j-^aind :-ia:i-i parallel lines, running longitudinally 



from end to end. At least this is 

 the ordinary arrangement ; but oc- 

 casionally you see scales, in which 

 there are two series of parallel lines, 

 arranged on either side of an imas-in- 

 ar}'" central line, towards which they 

 respectively converge, but never, I think, diverge from 

 it. These lines appear to form thickened ribs, but seem 

 to be made by elevations of the membrane both above 

 and below. Between the ribs, on the larger scales, we 

 see a number of very delicate cross lines, which are 

 probably regular wrinklings of the depressed surface. 



There is another little Insect of the same family, 

 commonly found in cupboards, and in chinks of old 

 damp houses, and called the Sugar-louse (Lepisma) ; 

 very much like this, but of a silvery lustre, and carrv- 

 ino- the three bristles of the tail diverging widelv. This 

 also is covered with scales, some of which are preserved 

 on this glass slide. Here, while the general appearance 

 and structure agree with those of the scales which we 

 have just been considering, there is considerable diver- 

 sitv in details. The form is usuallv ovate or shovel- 



