158 THE INDUSTRIES OF ANIMALS. 



in concealing its presence. Its habits have lately 

 been described by D. Cleveland of San Diego.^ In 

 the adobe land hillocks are numerous ; they are about 

 a foot in height, and some three or four feet in 

 diameter. These hillocks are selected by the spiders 

 — apparently because they afford excellent drainage, 

 and cannot be washed away by the winter rains — and 

 their stony summits are often full of spiders' nests. 

 These subterranean dwellings are shafts sunk ver- 

 tically in the earth, except where some stony obstruc- 

 tion compels the miner to deflect from a downward 

 course. The shafts are from five to twelve inches in 

 depth, and from one-half to one and a half inches in 

 diameter, depending largely upon the age and size of 

 the spider. 



When the spider has decided upon a location, 

 which is always in clay, adobe or stiff soil, he 

 excavates the shaft by means of the sharp horns at 

 the end of his mandibles, which are his pick and 

 shovel and mining tools. The earth is held between 

 the mandibles and carried to the surface. When the 

 shaft is of the required size, the spider smoothes and 

 glazes the wall with a fluid which is secreted by 

 itself. Then the whole shaft is covered with 

 a silken paper lining, spun from the animal's 

 spinnarets. 



The door at the top of the shaft is made of several 

 alternate layers of silk and earth, and is supplied 

 with an elastic and ingenious hinge, and fits closely 

 in a groove around the rim of the tube. This door 

 simulates the surface on which it lies, and is dis- 

 tinguishable from it only by a careful scrutiny. The 

 clever spider even glues earth and bits of small plants 



* Science, 20th January 1893. 



