WEAVERS OF ROUND WEBS. 



127 



downward and snstained by the feet, tlie difference being, as already noted, 

 that the Epeira clasps with her feet the meshed terminations of the radii 

 within the hub, while Acrosoma supports herself by the margin of the open 

 hub. In the case of Rugosa, the method is 

 the same but the position of the spider a little 

 different. The two hindermost legs are clasped 

 to the upper margin or to the bit of ribboned 

 lace that frequently runs upward from the hub 

 of the spiral space. The back or dorsum of 

 her abdomen thus hangs towards the ground. 

 The spinnerets are turned upwards and assist 

 to support the spider by a little dragline. The 

 head in this position is of course depressed, 

 and at an angle say of forty-five degrees, more 

 or less. She supports this part of her body not 

 only by the first and second pair, but 



Position j^jg^j |j ^l^g ^l^jj.j| .^|j. Qf 1p„j, which, 

 of Third ■^ ^ t, > > 



Legs. 



Fig. 112. Acrosoma mitrata suspend- 

 ed at the hub of her orb. 



Fourth 

 Legs. 



^"^ 



contrary to the custom of Orbweavers 

 generally, are thrown forward on either 



side of the face. Generally the third pair of 



legs is correlated with the fourth pair, and 



the second with the first, but here the third is associated with the first two. 

 The fact is doubtless in some way connected with the peculiar 



^°'^^ character of the fourth legs, which in the genus Acrosoma are as 



long as or longer than the first legs. The length of the fourth 

 pair is an evident convenience to the spider when walking ; for 



the ventral part of the abdomen is an inverted pyramid or cone, at the apex 



of which the spinnerets are placed. The ad- 

 ditional length of the fourth legs thus serves 

 to raise these organs above the ground as the 

 spider moves. The same reason, viz., the 

 length of the fourth legs, together with the 

 open hub, influences the position of the third 

 legs. These organs are not long enough to 

 clasp the marginal ring of the hub near the 

 feet of the fourth legs, and as there are no 

 cross lines in the hub to grasp as in the case 

 of Epeira, they must necessarily seek the 

 nearest place of rest, and thus are stretched 

 straight out from the body to the- side of the 

 hub, as is common with Mitrata (Fig. 112) 



and occasionally with Spinea ; or else are bent forward in the direction of 



the first and second pairs, and grasp the circumference of the hul), as docs 



Rugosa habitually and Spinea frequently. (Fig. 113.) 



Fig. 113. Acrosoma spinea in position 

 at the hub of her orb. 



