WEB-SPIDERS, 



223 



instance, the spinning instincts were directed solely to the protection of the species 

 during infancy, growth, and maturity ; and we may conclude that, apart from the 

 cocoon, the initial stage in the development of web-making was the formation of 

 some kind of tubular retreat. From this point the evolution of the spinning 

 industry perhaps the most important and interesting feature in the natural 

 history of spiders seems to have progressed 

 along two lines. Along one the tubular retreat 

 becomes gradually elaborated until it culmin- 

 ates in the trap - door nest ; while along the 

 other the tube is to a greater or less extent, or 

 even wholly, superseded by a new structure, 

 the snare ; the latter attaining its greatest 

 perfection in the triangular snap - net of 

 Hyptiotes, or the beautiful and symmetrical 

 orb -web of the common garden spider. At 

 the outset it is possible that the simplest form 

 of snare arose from the spinning of supporting 

 lines around the mouth of the tubular retreat, 

 and if these served to entangle prey it is clear 

 that a new and easy method of obtaining food 

 would be opened up, and the habit of spinning 

 webs of this nature would be fostered until 

 the various kinds of nets became evolved. 

 Another use to which the spinning of threads 

 may be put is that of flying. This is especially 

 practised by young spiders, who on fine 

 autumnal days climb to the tops of bushes 

 and fences, and, raising the abdomen into the 

 air, emit a thread or tuft of threads which 

 blowing away in the wind soon become large 



and strong enough to carry the spider, sometimes to great heights above the ground. 

 It was originally supposed that these threads were spun by a species called the 

 gossamer-spider, but it is now known that the habit is practised by young spiders 

 of different families. Floating about in the air, these fine threads meet and, 

 becoming entangled, form masses of web, which ultimately fall upon the bushes 

 and fields, sometimes covering them thickly with a white coating of fine silk. 



JAMAICA TRAP-DOOR SPIDER (Pachylomerus) 



AND APERTURE OF ITS NEST. 



SEGMENTED GROUP, Suborder Mesothelse. 



Spiders may be divided into the two main groups, Mesothelce and OpisthotJielce. 

 In the former, the spinning mammillae, eight in number, are situated in a cluster in 

 the middle of the lower surface of the abdomen; the upper surface of the latter 

 being covered with a series of nine dorsal plates, resembling those of scorpions, 

 while its lower surface is similarly furnished with two sternal plates covering the 

 first and second pairs of lung-sacs. In these characters the group differs from other 

 spiders, and in having the abdomen segmented it constitutes a kind of link 



