THE JOINTED ANIMALS 



FEMALE OF Drassus LAYING 

 HER EGGS. 



existing forms in having the abdomen protected 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 Aix satisfactorily testify. 



The females of all spiders lay eggs, from which the 

 young are subsequently hatched. The first act of the 

 mother before 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 form- 

 ing a cocoon. The cocoons differ greatly in shape and 

 color 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 wander- 

 ing species, the mother carries the 

 cocoon about with her, either attached 

 to her spinners or clasped between 

 her jaws. The young hatch ..inside 

 the cocoon, and subsequently make 

 their way to the outer world through 

 a rupture in its walls. They appear 

 in a helpless state, either clinging to- 

 gether in clusters, as in the Argiopidce; 

 staying in the nest, as in the jump- 

 ing spiders; or clambering on to their FEMALE OF WOLF SPIDER (Pardosa amentata) 

 mother's back, as in the wolf spiders. 

 During growth the skin is periodically 

 cast, the membrane of the cephalotho- 



rax splitting above the base of the limbs, and the carapace being raised to make 

 an aperture, through which the body with the new skin emerges. The young 

 spider is then soft, limp, and at the mercy of its enemies, until the integument be- 

 comes sufficiently hard and resisting to afford firm support to the muscles. Conse- 

 quently, during this time, many species seek shelter in silken tubes spun for the 

 purpose. On an average, perhaps, spiders undergo about eight or ten molts before 

 reaching maturity, which is attained during the period intervening between the 

 last molt and the last but one, so that the males and females, which during 



CARRYING HER COCOON. 



Below is shown the arrangement of the eyes when. 



seen from above. 



