THE LIFE OF THE SPIDER 37 



covering similar in texture to the base, and then cuts the biscuit- 

 shaped object loose from the floor and the scaffolding. This she 

 now seizes and holds beneath her cephalothorax and revolves slowly 

 by means of her palpi and legs. At first the spinnerets sew up the 

 edges between the two circular sheets until the break is scarcely 

 apparent. Then the mass is revolved in all directions and the spin- 

 nerets put down additional layers of silk until, as the sac is molded 

 and shaped, a nearly spherical object results. Soon after completion 

 of the sac, its white silk takes on a tinge varying from gray to 

 yellow, blue, or green; and the spider attaches the bag to her spin- 

 nerets. 



Many spiders spin this type of sac. The great flabby egg purses 

 of the tarantulas are prepared in the burrow and are guarded by 

 the mother until long after the young emerge. The delicate silken 

 bags of the trap-door spiders often hang from the side of their 

 burrow. The large lens-shaped bag of the huntsman spider is held 

 beneath the body by the female, who will not relinquish it without 

 a struggle. Many of the vagrant gnaphosids guard their eggs, but 

 others place their tough little sacs colored a shiny yellow, pink, or 

 red close against a rock or a chip of wood and leave them. 



The simplest type of egg sacs are those of the long-legged 

 pholcids and other primitive spiders, which use only a few threads 

 of silk to hold the mass together. The cosmopolitan Pholcus (Plate 

 XIX) glues her few eggs lightly and carries the mass in her cheli- 

 cerae. The tiny funnel-web tarantulas of the genus Microhexura 

 also carry their eggs in this manner, and thus minimize the need 

 for a strong sac. 



Some of the most marvelous and elaborate egg sacs are spun by 

 the sedentary spiders, which put their web-spinning superiority to 

 good use in constructing the coziest of egg cradles. The sac may 

 hang in plain view among the threads the central theme of the 

 web or it may be tied nearby to herbs or similar objects. Along 

 with the special attention accorded the precious egg mass goes a 

 somewhat different method of realizing the finished cradle. For 

 example: 



The large, pear-shaped sac of the orange Argiope (Plate 7), 

 which hangs near her web, is constructed in a most unusual manner. 

 Argiope always hangs downward from the threads of her slightly 

 inclined web, and her spinning activities are profoundly influenced 

 by this posture. A series of cross lines attached at several points 

 prepares a firm scaffold for the sac, which itself is a compound 



