WEB-SPIDERS. 



221 



account of its function as a jaw, and the remaining five the palpus. The mandibles, 

 too, are larger than in the Pedipalpi, and contain a poison-gland, opening at the tip 

 of the second segment, which is transformed into a strong fang. In the abdomen, 

 a marked character of most spiders is the absence of segmentation, its covering 

 consisting of a soft, hairy integument, or a hard horny cuticle, while on its 

 lower surface there are two pairs of shortened appendages, called the spinning 

 mammillce, upon which open the silk-glands. These mammillae are perhaps the 

 most distinctive feature in spiders. Although varying considerably in shape and 

 length, they are usually short and composed of two, or rarely three, segments. Each 

 spinning appendage, however, is primarily 

 composed of two branches, an outer and an 

 inner, the outer forming the two- or three- 

 jointed mammilla, while the inner branch 

 or intermediate mammilla is always one- 

 jointed. Consequently there may be as 

 many as eight mammillae ; usually, however, 

 there are but six, owing to the disappear- 

 ance of the inner branches of the first pair 

 of spinning appendages. 



The oldest known form (Arthrolycosa) 

 of the Carboniferous, differs from nearly all 

 existing forms in having the abdomen pro- 

 tected above by a series of plates, as in the 

 recent genus Liphistius, to which it was 

 doubtless allied. In Tertiary times, spiders 

 closely related to those now existing were 

 abundantly distributed over the Northern 

 Hemisphere, as their well preserved remains 

 from the Oligocene amber beds of the Baltic 



and from the gypsum beds of AlX Satis- 1, Foot with claws and hairs ; 2, Mandible with 



factorily testify. 



The females of all spiders lay eggs, from 

 which the young are subsequently hatched, 

 laying, is to spin a small and often saucer - shaped web. In this the eggs are 

 deposited, and are then covered over with two layers of silk forming a cocoon. The 

 cocoons differ greatly in shape and colour and texture, according to the spider that 

 makes them. They may be green, yellow, white, mottled, or nearly black ; round, 

 oval, lenticular, or cigar-shaped; soft and woolly, hard and nut-like, or smooth 

 like parchment ; while the outer casing is sometimes caked with earth or other 

 foreign material for purposes of concealment. After the construction of the cocoon, 

 the mother's interest in its fate varies in different spiders. Sometimes she pays 

 no further attention to it, as in the case of the garden spider (Araneus), which 

 suspends it in or near her web, and leaves the young to shift for themselves. 

 In some cases, again, she remains for a longer or shorter time on guard in its 

 vicinity, sometimes spinning a regular nest for her young and herself during this 

 period of quiescence ; but in other cases, especially among the wandering species. 



ANATOMY OF COMMON CROSS SPIDER 



diadema). 



poison-gland and duct ; 3, Face and jaws ; 4, Spin- 

 ning mammillae ; 5, One of the spinning papillae. 



The first act of the mother before 



