152 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



Protect- 

 ive 

 Apron. 



as 



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 

 around, giving the whole mass of spinningwork the appearance 

 of a hemisphere with the circular plane upwards, or of an in- 

 verted cone. The purpose of this apron is evidently protective, 

 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- 

 erably secure against attack 

 from that quarter at least. 



But the weavers of horizontal orbs have 110 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 serves 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. 143 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 



FIG. 142. Position of Orchard spider on its orb. 



