332 THE SPIDERS. 



again by the spiders. On the following day, however, he 

 found one of the holes again partly closed, the silken lining 

 being drawn across the opening of the passage from within. 

 The second cylinder was unchanged. The third was tempo- 

 rarily covered by three olive-leaves, spun together and 

 fastened by threads to the edges of the opening of the pas- 

 sage. Two days later a perfect movable door was made of 

 them. Thus each of the three spiders had acted quite dif- 

 ferently, each according to its own view and thought. How 

 could this be instinct ? 



The trap-door spiders very unwillingly leave nests which 

 they have once made. It has sometimes been observed that 

 nests turned completely upside down by the digging of the 

 ground are not left by their inmates, but are made habitable 

 again by carrying the tunnel to the surface of the ground 

 and the formation of a new door. In all cases no small 

 time and trouble are devoted to the formation of these 

 remarkable dwellings. The individual nests also only attain 

 gradually their full perfection and size, having at first, while 

 the spider is young and small, only the thickness of a crow- 

 quill, but being continually enlarged witli the growth of the 

 spider itself. The door also is increased bit by bit, and 

 thereby sometimes acquires the appearance of an oyster- 

 shell. On close investigation it is found to consist generally 

 of a large number of single layers of silk laid one over 

 the other, with earth between, and which are sometimes 

 as many as twenty or thirty. Sometimes, also, the old and 

 now too small doors are left and new ones made, so that we 

 may come across two or three of different sizes. It is obvi- 

 ously far more convenient and more advantageous for the 

 growing spider to continually enlarge and increase its nest, 

 than to make new nests time after time, for Moggridge has 

 noticed differences of size of from one to sixteen lines of 

 diameter, and the number of transitional nests would therefore 

 have to be very large. Howgreat must be the growth of spiders 

 is seen from an account of F. Pollock (" Ann. and Mag. of 

 Nat. Hist." for June, 1865), wherein a female Ejmra or 

 wheel-spider, after a lapse of eight months and ten or more 

 changes of skin, was 2,700 times as heavy as at her birth. 



The most common of the described forms of nests is that 

 of the simple non-ramified single door cork nest. There are 

 six different species, belonging to at least three genera, 



