xi] THERAPHOSID SPIDERS 95 



Now, however desirable occasional closure may 

 be, a permanent door would hamper the tarantula 

 in her hunting operations, but the habits of the trap- 

 door spider are different, and she closes her retreat 

 with a wonderful hinged lid or "trap-door." And 

 the commonest form of trap-door is also the most 

 perfect, being thick and tapering, and fitting ac- 

 curately into the bevelled f mouth of the tube like 

 a stopper in the mouth of a bottle. It is made of 

 alternate layers of spider silk and earth, and is free 

 for more than half its circumference, the remaining 

 portion of the surface disc being attached to the side 

 of the tube by a flexible hinge of silk. Moggridge 

 dissected the door of a full-sized tunnel into fourteen 

 graduated discs. The smallest and of course the 

 lowest represented the first door ever made by the 

 spider, and the successively larger discs indicated 

 the stages at which its increasing size rendered an 

 enlargement of the tube and therefore of the door 

 -necessary. 



The spider always interweaves vegetable matter 

 from the neighbourhood into each new disc, so that, 

 as a rule, it is entirely indistinguishable from its 

 surroundings when closed ; and not only dead 

 vegetable matter, for if the tube is situated amongst 

 moss, moss grows upon the lid. From our previous 

 experience, however, we shall not be surprised to 

 find that blind instinct and not forethought is 



