SPIDERS. 251 



what age spiders will attain ; some have been known 

 to live four years. 



" Under the guidance of their respective instincts," 

 says Mr. Blackwell, " a high degree of skill and in- 

 dustry is displayed in the construction of their retreats. 

 Many species occupy holes formed by themselves 

 beneath the surface of the earth, some of which, of a 

 cylindrical shape, are lined with a compact tissue of 

 silk, and have the entrance closed by a valve, pro- 

 vided with a hinge, which can be opened and shut at 

 pleasure. .Other species fabricate in the crevices of 

 walls, the crannies of rocks, beneath stones, on the 

 leaves of vegetables, and under the exfoliating bark of 

 trees, tubes, cells, or domes of silk, on whose exterior 

 surface-soil minute pebbles and other heterogeneous 

 materials are frequently distributed. A Theridion 

 fabricates a slender conical tube of silk, of a very 

 slight texture, measuring from one and a half to two 

 and a half inches in length, and about half an inch in 

 diameter at its lower extremity. It is closed above, 

 open below, thickly covered externally with bits of 

 indurated earth, small stones, and withered leaves and 

 flowers, which are incorporated with it, and is sus- 

 pended perpendicularly by lines attached to its sides 

 and apex, in the irregular snare constructed by this 

 species. In the upper part of this singular domicile 

 the female spins several globular cocoons of yellowish- 

 white silk, of a slight texture, whose mean diameter is 

 about one-eighth of an inch, in each of which she 

 deposits from twenty to sixty small spherical eggs, 

 of a pale yellowish-white colour, not agglutinated 

 together. The young remain with the mother for a 



