WEBS OF SPIDERS. 135 



plied by 24, being the mean number of circumvolutions 

 formed by the spiral line, will give 3360, being the num- 

 ber of globules contained on all the lines between two con- 

 tiguous radii : this number, being again multiplied by 26, 

 the mean number of radii, produces 87,360, the total num- 

 ber of viscid globules in a finished net of average dimensions. 

 But larger nets, by a similar calculation, will contain up- 

 wards of 120,000 viscid globules, and yet the time occupied 

 in the construction of this net is not more than forty minutes. 

 Moreover, the threads with which the spider composes the 

 retreat in which it takes up its abode, or the nest in which it 

 envelopes its young, do not appear to be of the same nature 

 as the net-threads, neither are the threads of which it forms 

 the case for its young similar to the former, the texture of 

 these cases being in some species quite firm and smooth, re- 

 sembling parchment. This case is also sometimes covered 

 with a coating of loose flossy silk, which also seems of a dif- 

 ferent texture : hence it is evident that the vessels at the 

 extremity of the abdomen, which serve for the secretion of 

 the silk, as well as the structure of the spinnerets and spin- 

 nerules, require a much more minute investigation than has 

 hitherto been given to them, in order to discover the precise 

 manner in which these various kinds of silk are elaborated 

 and discharged. 



The web of Epeira diadema is one of the most beautiful 

 and most common of the spider constructions in this country, 

 being found in every bush or tree, between hedges and 

 shrubs, &c., during the autumnal months. The top line of 

 this web appears to be first spun, either by attaching a thread 

 as above described, and then carrying it along until it is of 

 sufficient length, when it is attached to some adjacent object 

 to which the spider has crawled, or by throwing out a float- 

 ing line, whilst the spider remains stationary, the action of 

 the air carrying this line on until it becomes attached to 

 some object, when, in either case, it is doubled and re- 



