The Life of Spiders 



we have now to consider the nature and uses of the different kinds 

 of silk. 



The dragline. — Most spiders as they move from place to 

 place spin a thread, which marks their course; this thread has 

 been termed the dragline. Draglines are the most commonly 

 observed threads of spiders; it is by them that spiders drop from 

 an elevated position to a lower one; it is of them that the irregular 

 nets are largely composed; and the foundation of an orb-web is 

 made of draglines. 



There is a commonly accepted error regarding the structure 

 of a dragline. As the number of spinning tubes is large in the 

 spiders most commonly studied, the orb-weavers, it has been 



inferred that in spinning a line the 

 spider emits a delicate thread from 

 each, and that all of these, some- 

 times several hundred in number, 

 blend into one. This is not the case; 

 the dragline is composed of a small 

 number, usually only two, compara- 

 tively large threads. These, judging 

 by their size are evidently spun from 

 spigots. 



The attachment disks. — If a spider 

 that is running along some object and 



Fig. 184. . . ii- • j_ i_ 



an attachment disk spinning a dragline as it goes be 



carefully observed, it will be seen to 

 fasten this line at frequent intervals to the object on which it 

 is. This is done by making what may be termed an attachment 

 disk; such a disk is pictured by Fig. 184; it is composed of 

 a large number of minute looped threads. 



The method of making an attachment disk can be easily 

 observed by enclosing a living spider in a bottle, and watching 

 it with a lens as it fastens its dragline to the sides of the bottle. 

 This I have done many times; and in all of the cases that I have 

 observed, the spider applied the fore spinnerets to the surface 

 of the glass and by quickly spreading the organs apart and bring- 

 ing them together again two or three times made the disk. An 

 examination of the disk with a microscope shows that it is com- 

 posed of a large number of fine threads. It is evident therefore 

 that the silk of which it is made issues from the numerous small 



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