THE GENESIS OF SNARES. 341 



point at which the inward end of the Hne is fastened to the tent or stays. 

 But this loop is only incidental, and serves no special purpose (as far as 

 we know) in securing the entanglement of prey. But with the Triangle 

 spider the coil is a prominent and special feature of the net. It is always 

 found between the hind legs and the third pair of legs, and when the 

 snare is sprung, as already described, this coil instantly straightens out, 

 permitting the whole net to shoot forward, and the forward motion sends 

 every line around the entangled victim and adds to the degree of its en- 

 tanglement. 



When we consider the Ray spider's habit we find the trapline here 



even more highly specialized. It has, first, the uses common to the typical 



Orbweaver, that is to say, it serves for telegraphy and transi- 



■^^7 , tion. Second, it acts as a regular tra[), inasmuch as it has a 



m T ])rominent coil of slack line readv to be sprung at any time. 

 Traphne. i, ^ , . . " r- f i • 



But, further, it unites all the separate sectors of the orb into one 



common system, thus serving not only to spring a single net, as in the case 



of Hyptiotes, but a series of united nets of the same sort. 



Moreover, this spider possesses the habit of moving its trapline from 

 point to point, instead of keeping it fixed as in the case of the Triangle 

 spider — certainly a remarkable adaptation. Further, by a simple but ingen- 

 ious system of "locking" the web, that is, twisting the axis of the sev- 

 eral rays around the extremity of the trapline, the spider causes the trap- 

 line to hold her whole snare in workable position while she resorts to 

 any part thereof to seize her prey. Thus, also, as the daily wear and tear 

 in capturing food destroys in succession various parts of the web, the 

 trapline holds together and intact the remaining parts, even though quite 

 opposite to each other. 



We have thus traced the natural history of this important and useful 

 member of the Orbweaver's web, from a simple dragline by which the an- 

 imal escapes from and returns to her snare, through an interesting series 

 of variations, to this quite specialized and complex use which marks the 

 trapping habit of Thcridiosoma gemmosum. 



Thus, as a dragline it serves, first, the cautionary use of escape from 

 danger by swinging to an anchorage ; second, it affords a trail for retreat 

 to the place of departure ; third, it serves to telegraph agitation 

 of the snare to the proprietor ; fourth, it holds the snare taut, 

 and thus maintains its efficiency ; fifth, it acts as the spring line of a 

 genuine trap ; and, sixth, it binds and locks together the united or the dis- 

 severed parts of a snare, which at the same time it also springs separately 

 or together as need requires. Of course, I do not pretend to intimate that 

 there has been anything like a development of the use of the trapline in 

 the sense that there is any traceable genetic connection between the various 

 adaptations here pointed out. So far as I know, and, perhaps, as far as 

 can be known, every species preserves its own habit quite independent of 



