SPIDEES AUD MITES. 



255 



The upper portion of the mouth is formed by two 

 stout mandibles, which are jointed to the front of the 

 head, and can be either widely expanded or brought 

 together so as to form a covering to the labium. They 

 are pincer-form, like the claws of a crab, the two fin- 

 gers being strongly toothed on their opposing surfaces. 

 Tliey thus form effective prehensile instruments. These 

 mandibles can be advanced separately or together, and 

 the Avhole head can be elevated or depressed. 



HEAD OF CHEESE-MITE. 



In the water of ponds we may frequently see, play- 

 ing among the sub-aquatic vegetation, bright-coloured 

 Mites ; sometimes rich velvety green, sometimes pur- 

 ple, but more commonly brilliant scarlet ; often curi- 

 ously marked with sinuous patterns or spots of black. 

 They swim rapidly and evenly by means of rapid row- 

 ings with their legs, which are thickly fringed with 

 long hau's. I have one here, which seems to be the 

 Syd/rachna hist/rionica. It is a little, flat, circular, 

 cushion- or cake-like creature, scarlet, with four clouds 



