DWELLINGS. 1 59 



on the upper side of his trap-door, thus making it 

 closely resemble the surrounding surface. 



The spider generally stations itself at the bottom 

 of the tube. When, by tapping on the door, or by 

 other means, a gentle vibration is caused, the spider 

 runs to the top of his nest, raises the lid, looks 

 out and reconnoitres. If a small creature is seen, it 

 is seized and devoured. If the invader is more 

 formidable, the door is quickly closed, seized and 

 held down by the spider, so that much force is 

 required to lever it open. Then, with the intruder 

 looking down upon him, the spider drops to the 

 bottom of his shaft 



It has been found by many experiments that when 

 the door of his nest is removed, the spider can renew 

 it five times — never more than that. Within these 

 limitations, the door torn off in the evening was found 

 replaced by a new one in the morning. Each suc- 

 cessive renewal showed, however, a greater proportion 

 of earth, and a smaller proportion of silk, until finally 

 the fifth door had barely enough silk to hold the 

 earth together. The sixth attempt, if made, was a 

 failure, because the spinnarets had exhausted their 

 supply of the web fluid. When the poor persecuted 

 spider finds his domicile thus open and defenceless, 

 he is compelled to leave it, and wait until his stock of 

 web fluid is renewed.^ 



Skilful diggers prepare burrows with several en- 

 trances; some even arrange several rooms, each for a 

 special object. The Otter seeks its food in the water, 



^ The Trap-door Spiders of various parts of the world have been 

 carefully studied, and the gradual development of their skill traced 

 through various species, by Eugene Simon ; see, for example, Actes de 

 la Soc. Lin. de Bordeaux, :888. 



