194 AN INTRODUCTION TO ZOOLOGY. 



The little red mite called the harvest bug, and the 

 itch insect, may be mentioned as other forms which 

 attack man. Other mites produce galls on plants: 

 these galls may be known from those produced by 

 insects by the fact that they are not closed ; but ou 

 turning up the leaf, you find that it is merely thick- 

 ened and gathered up in a blister, to form the gall. 



The various Mites, and some other forms, including 

 Fentastomwn, a degraded parasitic form which is found 

 in the head of the dog, are sometimes classed together 

 as Lipobranchiata, or Arthropods that have no gills. 



The true Spiders have the body divided into two 

 regions composed of fused segments : the thorax, which 

 bears eight legs and is joined with the head, and the 

 abdomen. They breathe with lungs, the openings 

 to which are situated on the abdomen. The spin- 

 nerets, or glands which secrete the thread for the 

 web, are placed at the end of the abdomen. There 

 are a number of simple eyes, eight in most families, 

 but six in others. A poison gland is placed in the 

 first pair of claws (called the chelicerse). The 

 different kinds of spiders construct their nests ac- 

 cording to many different patterns. Some spiders, 

 found in France and elsewhere, make a web in the 

 earth, with a lid to it, furnished with a hinge ; others 

 make web lids to their nests ; others make long 

 tubular nests in the ground. The nest of the ordinary 

 house-spider may be studied anywhere : if it be dis- 

 tui'bed and broken from its attachments, the mother 

 spider will take it up with her claws and carry it to 



