VARIATION IN WEBS OF SPIDERS. 137 



spine inserted near the termination of the tarsus of each 

 posterior leg on the under side, which curves upwards at its 

 extremity, and which, by the action of the flexor muscles, is 

 brought in immediate opposition to the claws, by means of 

 which the animal is enabled to hold with a firm grasp such 

 lines as it designs to attach itself to ; and hence it is obvious 

 why these spiders usually direct their heads downwards when 

 they occupy the centre of their nets. 



Spiders, in regard to the construction of their webs, may 

 be naturally divided into two great groups, which have been 

 named the sedentary and the wandering spiders. The latter 

 do not construct regular webs, but either live a vagabond 

 life, as the genus Salticus, or merely throw out a few loose 

 and irregular lines in the neighbourhood of their nest. The 

 sedentary spiders comprise two divisions those which form 

 nets and those which weave webs. The net-weavers are 

 again divided into the geometric species, and those which 

 construct webs of an irregular form, the meshes being at 

 certain distances apart, but not arranged in concentric circles. 

 This group, which is in general composed of minute spiders, 

 is the most curious on account of the singular and astonish- 

 ing variety in the operations of the species of which it is 

 composed. The genus Theridion may be mentioned as the 

 typical group. The web-weavers spin a closer material than 

 the former, and, like the net-spinners, are divisible into two 

 groups, the cloth-weavers, which suspend their hair or mat- 

 like webs horizontally between plants without any circular 

 retreat (genus Linyphia, &c.), whilst the other section may 

 be called tapestry-workers, suspending their webs in the 

 angles of walls, &c., furnished with a circular retreat formed 

 like the rest of the web. The domestic spider is an example 

 of this division. 



During the summer and early autumn months, it is not an 

 uncommon circumstance to observe numerous long floating 



x3 



