THE TRUE OR WEB SPIDERS 



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growth are much alike, emerge from the final casting in a fully developed state. In 

 this stage the two sexes are distinguishable, the female having the palpi normally 

 constructed, while in the male the terminal segment of this appendage carries on its 

 lower surface an organ which in its simplest form is somewhat flask shaped, but 

 is more often variously modified and complicated. The male, also, is generally 

 rather the smaller of the two, sometimes indeed, as in many tropical members of the 

 family Argiopidce, being of quite insignificant size in comparison with the female. 

 He also has longer legs and a thinner abdomen, being thus the more graceful and 

 active of the two. In the most sedentary of all spiders, or those belonging to the 

 families Thcridiidce and Argiopidcc, still more striking differences often occur, the front 

 part of the carapace being sometimes raised into a high pinnacle-like outgrowth. 

 When the two sexes are approximately equal in size, the male is comparatively safe from 

 his spouse during the period of courtship, but when, as in the Argiopidce, he is much 

 the weaker of the two, the female often avails herself of her superiority in size and 

 strength to devour her mate. The first uses of the silk glands seem to be to supply 

 material for the construction of the cocoon, and of a tent or tubular retreat for 

 the protection of the mother and young, or for the latter when passing through 

 the dangers attendant upon the casting of the skin. Such cases are also used for 

 the same purpose by many species during the winter months in temperate latitudes, 

 and during drought in more tropical climes. It thus appears that, in the first 

 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 re- 

 treat. From this point the evolution of the 

 spinning industry perhaps the most impor- 

 tant 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 culmi- 

 nates in the trapdoor 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 even wholly, superseded by a new structure, 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 JAMAICA TRAPDOOR SPIDER (Pachylom- 

 webs of this nature would be fostered until erus} AND APERTURE OF ITS NEST. 



