The Structure mid Habits of Spiders. 23 



The spinning-glands, u, lie above the spinner- 

 ets, and along the under side of the abdomen. 

 They will be more fully described in the chapter 

 on spinning. 



POISON-GLANDS. 



The poison-glands, n, are partly in the basal 

 joints of the mandibles, and partly in the head, 

 and discharge by a tube which opens at the 

 point of the claw of the mandible, Fig. 15, a. 



CLASSIFICATION. 



There is not room in this book to explain the 

 classification of spiders into genera and species; 

 but a description of the following well-marked 

 groups, which contain nine-tenths of all spiders, 

 will give a general idea of the differences among 

 them, and help to understand what follows. 



MYGALIDyE. 



This family includes the largest known spi- 

 ders. The body is usually very hairy and dark- 

 colored. Most species have only four spinner- 

 ets ; and one pair of these are long, and are 

 turned up behind the abdomen. They have 



