SPIDERS AND MITES 247 



that of our abundant Garden Spider, for instance. You 

 have observed the cables which stretch from wall to wall, 

 or from bush to bush, in various directions, to form the 

 scaffolding, on which the net is afterward to be woven; 

 then you have marked the straight lines, like the spokes 

 of a wheel, that radiate from the centre to various points 

 of these outwork cables, and finally the spiral thread that 

 circles again and again round the radii, till an exquisite 

 net of many meshes is formed. 



But possibly you are not aware that these lines are 

 formed of two quite distinct sorts of silk. It has been 

 shown that the cables and radii are perfectly unadhesive, 

 while the concentric or spiral circles are extremely viscid. 

 Now the microscope, or a powerful lens, will reveal the 

 cause of this difference; the threads of the cables and radii 

 are perfectly simple, while the spiral threads are closely 

 studded with minute globules of fluid, like drops of dew, 

 which, from the elasticity of the thread, are easily sepa- 

 rated from each other. These are globules of viscid gum, 

 as is easily proved by touching one or two with the finger, 

 to which they will instantly adhere ; or by throwing a little 

 fine dust over the nest, when the spirals will be found 

 clogged with dirt, while the radii and cables remain un- 

 soiled. It is these viscid threads alone that have the 

 power of detaining the vagrant flies which accidentally 

 touch the net. 



The diversity of the secreting organs already alluded 

 to, as well as in the spinnerets, is no doubt connected with 

 this difference in the character of the silk ; and it is worthy 

 of remark that this diversity is greatest in such Spiders, 

 as the Epeirce, which spin geometric nets. 



Immense is the number of globules of viscidity that 



