(.KXKKAL CHARACTERISTICS OF ORBWEAVERS' BNABE8. 



55 



E- t 



and a close observation of her feet will show that the claws grasp, and 

 even draw out somewhat the lines which represent the radii continued. 



Every motion of the net is thus communicated more readily 

 Meshed tnrough t ] ie taut n nes to the sensitive feet. The brushes or 



tufts of delicate hairs with which these organs are provided, 

 and which are in contact with the lines, must greatly increase the sensi- 

 tiveness of the creature to every movement. 



This natural telegraphy is, perhaps, also aided by a short line extend- 

 ing from the spinnerets to the upper part of the hub. This line is apt 

 to divide into two, or radiate into several branches near the hub. In this 

 position, of course, the apex of the spider's abdomen is slightly elevated 

 (Fig. 51). However, the chief design of this habit is probably to hold the 

 aranead to her snare when she rushes after her 

 prey, or to give her a point of attachment for 

 dropping out of the web, or running from it in 

 case of assault, with similar advantage when she 

 may wish to return. 



2. The Sheeted Hub is wholly covered by a 

 closely woven sheet of white silk, against which 



the under part of the spider is placed 



as she hangs thereon. The type of 



this form of hub is that made by the 

 Basket Argiope, A. cophinaria, (\Valck.), the largest 

 and one of the most beautiful of our indige- 

 nous Orbweavers. It is shown at Fig. 52, where 

 a thick, irregular shield like piece two inches long 

 and one and a half wide, covers the entire hub. 

 Above, it extends in a broad ribbon of the same 

 consistency to the spiral space, a distance of 

 one and seven-eighths inches ; and below, it terminates in a narrow, zigzag 

 ribbon two inches in length. (Fig. 52.) 



3. The Open Hub is entirely free from any spinningwork, being a 

 small opening in the centre of the orb, that is, the point toward which 



the radii tend. It is characteristic of snares spun by the genus 

 Acrosoma, and prevails largely in horizontal orbs. But it is 

 frequently found in the webs of spiders whose general habit is 

 to spin a meshed hub. Such variation in habit of course prevents us 

 from taking these peculiarities of the hub as characteristics of absolute 

 determinative value. Nevertheless, they are valuable, and will 

 be found generally distinctive. The Notched Zone (NZ, Fig. 

 49) is a short series of spiral lines, ordinarily from four to ten 

 in number, immediately surrounding the hub. These spirals do not 

 cross the radii directly, but diagonally, thus causing a notch or angle 

 on each side when they are drawn taut. In other words, the spiral line 



at her 



pen 





