3 8 AMERICAN SPIDERS 



structure. First, yellowish threads are laid down to form a roughly 

 rectangular roof, and on this the female spins a thick tuft of fluffy 

 yellowish silk, which forms an irregular mass above her. Into this 

 yielding feather bed she next spins a firmer sheet of dark brown 

 silk, comparable to the base in which Pardosa places her eggs, and 

 which serves the same purpose for Argiope. She lays the eggs up- 

 ward against this brownish sheet by forcing the viscid liquid and 

 the many hundreds of eggs through the genital orifice. (Most of the 

 sedentary spiders that hang downward from webs, and even some 

 of the vagrants that run upright, defy gravity by depositing their 

 eggs in this strange manner.) The egg mass hangs as a yellow 

 spherical ball, and over it Argiope spins a thin but tough covering 

 of whitish or yellowish silk, which is joined to the brown silk disc. 

 Around the whole mass the eggs, their covering, and the rectan- 

 gular roof she then spins a fluffy covering of rusty brown or yel- 

 lowish brown silk, very loosely packed, which forms a voluminous 

 blanket around the egg mass. These lines are spun with the aid 

 of the spider's hind legs, which comb them out of the hind spin- 

 nerets in loose loops and pat them down into the mass. Over the 

 spongy padding Argiope now puts down a more finely spun cover- 

 ing of white or yellow silk, largely made by using the hind spin- 

 nerets alone. Smooth and closely spun, this outer covering hardens, 

 becoming a dry yellowish or brownish cover that crackles like 

 parchment. 



The orange Argiope thus produces, after several hours of tireless 

 spinning, six different sheets, tufts, or covers and from them makes 

 three envelopes for her eggs a thin white inner fabric, a thick 

 woolly or flossy blanket, and a tough outer cover. The innermost 

 layer is essentially the same as that spun by Pardosa and many other 

 spiders, and is composed of two parts, the sheet that receives the 

 egg mass and the cover. 



In some orb weavers, the sac is drawn out into a short or long 

 neck or stalk. Mastophora hangs her sac (Plates III and XXIII), a 

 globular bag with a thick stalk once or twice its length, on twigs 

 and leaves near her nest. It is doubtful that the stalk contributes in 

 any way to the security of the eggs, since the sac is easily available 

 to any insects that can reach the twigs. In many instances, Masto- 

 phora lashes the base of her sac directly to the twig. In some other 

 spiders, however, the ball of eggs is suspended in midair by a thread 

 of silk. The pale brown bag of Ero, with its irregular covering of 

 brownish silk, hangs on an inch-long pedicel in a cavity beneath 



