SProEKS AND MITES. 249 



toucliins^ one or two with tlie fiiio^er, to which thev will 

 instantly adhere ; or hy throwing a little fine dust over 

 the nest, when the spirals will be found clogged M'ith 

 dirt, while the radii and cables remain nnsoiled. It is 

 these viscid threads alone that have the power of de- 

 taining the vagrant flies which accidentally touch the 

 net. 



The diversity of the secreting organs already al- 

 Inded to, as well as in the spinnerets, is no doubt con- 

 nected with this diiFerence in the character of the silk ; 

 and it is worthy of remark that this diversity is 

 greatest in such Sjjiders, as the Epeirce^ which spin 

 geometric nets. 



Immense is the number of globules of viscidity that 

 stud the spiral circles of one of these nets. Mr. Black- 

 wall, the able and learned historian of the tribe, has 

 estimated that as many as 87,360 such pccirly drops oc- 

 curred in a net of average dimensions, and 120,000 in 

 a large net of fourteen or sixteen inches diameter ; and 

 yet a Spider will construct such a net, if uninterrupted, 

 in less than three-quarters of an hour. 



Scarcely less admirable is the ease and precision 

 M'ith which the little architect traverses her perpendic- 

 ular or diagonal web of rope ; a skill which leaves that 

 of the mariner who leaps from shroud to backstay in a 

 ship's rigging immeasurably behind. To understand 

 it, however, in some measure, look at this last joint of 

 one of the feet of our well-used Cliibiona. It is a cylin- 

 drical rod, ending in a rounded point ; every part of its 

 surface is studded wdth stiff, rather long, horny bris- 

 tles, which, springing from the side, arch inward to- 

 wards the point. ]^ow this array of spines effectually 

 prevents a false step, for if any part of the leg, which 

 11* 



