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152 AMERIGAN SPIDERS AND THEIR SPINNINGWORK. 
situations, spun upon branches and stalks of tall weeds and grasses, or in 
the lower branches of shrubs, bushes, and trees. The orb is frequently 
quite round, indeed is habitually round when spun in open spaces where 
the spider’s action is unfettered. An adult spider’s orb has an average 
diameter of from eight to nine inches. The spirals and radii are closely 
placed and average in number about thirty. The hub is open and the 
spider has its position just beneath, clinging back downward to the margin 
of the hub or to the notched zone immediately surrounding it. The abdo- 
men is often turned upward almost at right angles to the cephalothorax, 
and is stayed by a line attached to the orb above. Fig. 142. 
From the foundation lines of the orb downward there usually extends 
a mass of crossed lines, which may be called the apron. These are thick- 
est upon two sides, although sometimes they extend entirely 
Protect- ground, giving the whole mass of spinningwork the appearance 
ive : : ‘ ; 
of a hemisphere with the circular plane upwards, or of an in- 
Apron. 
verted cone. The purpose of this apron is evidently protective, 
as it must shield the spider from assaults of enemies that would be 
inclined to strike her as 
she hangs beneath her orb. 
Spiders occupying vertical 
orbs which for the most 
part are swung upon foli- 
age and other objects which 
form a background, are tol- 
Fic. 142, Position of Orchard spider on its orb. erably secure against attack 
from that quarter at least. 
But the weavers of horizontal orbs have no such natural local protection. 
Hence it is the more needful that they should manufacture one for 
themselves. The apron may also stay the foundation lines that support 
the delicate work of the orb itself, and perhaps protects it from the ap- 
proach of insects who would break through without giving the spider 
an opportunity to catch them. It doubtless also seryes for the arrest of 
insects, as I have found flies entangled upon the threads. It may thus, as 
in the case of the Labyrinth spider, be of some benefit to the occu- 
pant in the way of providing food. But for this the principal reliance is 
of course upon the orb, and the chief supply is from those insects that 
strike it as they fly downward. ‘The outside foundation lines, to which 
the horizontal orb is hung, are sometimes of considerable length; I have 
found them thirty-six inches long. Fig. 148 is an accurate representa- 
tion of the foundation system of the Orchard spider, and also a section of 
the snare showing the spiral system as well as the central space. The lines 
are drawn vertically, but, of course, the reader will understand that they 
are to be considered as spun horizontally as they were in nature. A little 
better view of the central space is shown at Fig. 144 where the delicate 
