SPIDBKS AND MITES. 



221 



must put a drop of water between the plates, in order to 

 wash away the opaque granules which will escape from the 

 bodies of the animals ; after which the skin, and all the 

 solid parts, will be left beautifully clear and distinct. 

 Moreover, by putting half-a-dozen specimens in at once 

 we shall secure them pressed in various aspects, and be 

 pretty sure of some perfectly flat and symmetrical. 



I have one under such conditions ; the parts of the 

 mouth nicely expanded, and the whole well displayed. 

 Now for a high power ; for, to discern this properly, we 

 cannot do with less than 600 diameters. 



HEAD OF CHEESE-MITE. 



Viewed from beneath, we see a broad labium, nearly 

 square, divided at the tip into two blunt points, with a 

 sharp notch between them. The two lateral edges are, as 

 it were, buttressed by the pair of palpi, which are thick, 

 and consist of four joints each ; these are distinguished 

 by the bristles at each joint, though the whole are united ; 

 soldered, as it were, to the sides of the lip. 



The upper portion of the mouth is formed by two stout 

 mandibles, which are jointed to the front of the head, and 



