WEAVERS OF ROUND WEBS. 



127 



Position 

 of Third 

 Legs. 



Fk;. 112. Acrosoma mitrata suspend- 

 ed at the hub of her orb. 



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



tbat 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 

 also by the third pair of legs, which, 

 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 



Legs. ^°^S ^s 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 enougli 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 grasj) as in the case 

 of Epeira, they must necessarily seek the 

 nearest place of rest, and thus are stretched 

 straight out from tlie body to the side of the 

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



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



the first and second pairs, and grasp the circumference of the hub, as does 



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



Fir,. 113. Acrosoma spinea in position 

 at the hub of her orb. 



