128 TRAP-DOOR SPIDERS. 



It seems to be the rule with spiders generally that 

 the offspring should leave the nest and construct 

 dwellings for themselves when very young. 



Mr. Blackwall,"'^ speaking of British spiders, says : — 

 " Complicated as the processes are by which these 

 symmetrical nets are produced, nevertheless young 

 spiders, acting under the influence of instinctive im- 

 pulse, display, even in their first attempts to fabricate 

 them, as consummate skill as the most experienced 

 individuals." 



Again, Mr. F. Pollockf relates of the young of 

 Ujjeii'a aurelia, which he observed in Madeira, that 

 when seven weeks old they made a web the size of 

 a penny, and that these nets have the same beautiful 

 symmetry as those of the full-grown spider. Those 

 of the latter are vertical, circular, made of about 250 

 feet of thread, having about 35 radial lines and 38 

 concentric circles, the outermost of which is some 20 

 inches in diameter. After the lapse of a day or two 

 the web loses its adhesive property and a new one is 

 made. In about six months the female Epeira has 

 completed her ten changes of skin, one of which takes 

 place in the cocoon, and " at the end of eight months 

 the spider is 2700 times as heavy as at its birth." 

 This ^czr« lives, we are told, for about eighteen months. 



One can scarcely contemplate the work of these 

 architects and weavers, and especially of the trap-door 

 makers, without being carried away into the whirlpool 

 of discussion which has so long raged round the word 

 instinct. 



* Loc. cit., p. 11. 

 + The History and Habits of Epeira aurdia, in Annals and Mag of Nat, 

 Hist, for June, 1865. 



