GENERAL CHAKACTEIIISTICS OF OKBWEAVEKS SNAKES. 



55 



Meshed 

 Hub. 



Sheeted 

 Hub. 



and a close observation of lier feet will show that the claws gras}), and 

 even draw out somewhat tlic linos which represent the radii continued. 

 Every motion of the net is thus connnunicated more readily 

 through the taut lines to the sensitive feet. The brushes or 

 tufts of delicate hairs with wliich 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 tliis 

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

 (Fig. 51). However, the chief design of this habit is [n-obably 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, (Walck.), 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 0})en 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 si)un 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, the}- are valuable, and will 

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

 49) is a short series of s]>ir;il lines, ordinarily from four to ten 

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

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

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



Fig. 51. Spider suspended at her 

 hub, Argiope argyraspis. 



Open 

 Hub. 



Notched 

 Zone. 



