160 NATURAL HISTORY. 



thus fastening the door so tightly that it will be torn before it can be 



pulled open. 



The trap-door spiders excavate their homes by means of the small 

 appendages in front, carrying away the earth grain by grain. When the 

 tube is deep enough, the door is formed. To make this, the spider spins a 

 few threads across the top of the tube, and then covers these with earth, 

 and then more threads and more earth are added until the whole is of the 

 proper thickness. At first the supporting threads of the door extend 

 across the tube in all directions ; but as soon as the door is so far advanced 

 as to be able to retain its shape, these threads are bitten away all around 

 except where they are left for the hinge. After this the rest of the work 

 is devoted to finishing the inside of the door. 



Some of the European species studied by Moggridge lived in mossy 

 localities, and these of course covered the doors of their tubes with moss 

 like that around them. The question arose, was this a habit or a result of 

 reason ? To test it, our author took away all the moss from the vicinity of 

 one of the holes, and then destroyed the door. The spider soon con- 

 structed a new door, and answered his question by bringing moss from a 

 considerable distance to cover it. In this way the door, instead of being 

 concealed, was the most conspicuous object in the neighborhood. 



With some of the species it would seem that the protection and conceal- 

 ment afforded by the trap-door was not sufficient, as some construct a second 

 door some distance inside the tube, so that one would suppose that he saw 

 the bottom. Others make a branch to the main tube, and hang a door 

 over the junction of the two, so that the observer would not suspect its 

 existence. It is difficult to imagine the way in which these and other 

 habits have arisen. Did not the animals go so far, an explanation would 

 be easy ; but so varied, so complex, are some of the features, that one cannot 

 readily conceive a cause adequate to produce such results. 



Farther north a somewhat similar habit to that of the trap-door spiders 

 has been observed. The spider digs its hole in the sandy soil, lines it with 

 a delicate, silken web, and surrounds the mouth of the nest with a ring 

 of leaves and twigs fastened together with silk. Others vary it by build- 

 ing up the ring of twigs alone arranged like the timbers in a log-house. 



We have already alluded once or twice to spider silk, but the subject 



denial ids far more attention, as spinning is highly characteristic of spiders, 



v as the careful housewife well knows. Some spin but scattered threads, 



others silk, with which they form cocoons for their eggs, while still others 



form the familiar webs with which they capture their prey. 



The spinning-organs are placed on six or eight elevations on the 

 hinder lower surface of the abdomen. On each of these ' spinnerets ' are 



