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THE AMERICAN NATURALIST [Vol. XLI1 



ers and not snarers, and particularly for the diurnal At- 

 tidae as demonstrated by the studies of the Peckhams. 6 

 But among the snare-weavers I feel positive, in agree- 

 ment with McCook 's conclusions, that the sense of touch 

 almost completely supplants that of sight. Long obser- 

 vation in the field and especially upon species kept 

 under control has led me to this opinion, the main rea- 

 sons for which may be briefly mentioned. The lines of the 

 snare are the medium by which the spider secures its food 

 and conducts its mating, all by touch. In the operation of 

 spinning, whether it be a snare or a nest or a cocoon, 

 the process is conducted beneath the ventral surface 

 of the spider, accordingly, in a position removed from 

 its field of vision; and all such architecture is frequently 

 carried on in the dark of night. With the true orb-weav- 

 ers, the argiopids, the spider sometimes remains at the 

 center of the orb holding tensely with its tarsal claws 

 various radii and thereby feeling any object that strikes 

 the web. In this position she can see only a small part 

 of the snare, if any of it, yet she instantly perceives any 

 impact upon any part of the snare. Or the spider does 

 not rest upon the snare at all, or comes out upon it only 

 at night and twilight, remaining in a nest at some dis- 

 tance from the snare; in that case the spider perceives 

 any shock to the snare by means of the trap-line that 

 passes from her claws to the center of the snare, such a 

 trap-line being a modified radius. McCook (I. c.) has 

 given an admirable treatment of the use of this trap-line 

 and of how it is often employed to spring the snare. Thus 

 Epeira marmorea remains through the hours of sunshine 

 for the most part in a nest within a leaf that has curled 

 up, where she can not see the web at all, and feels every 

 motion of it through the connecting trap-line. And it is in- 

 structive to watch her when an insect agitates the snare. 

 She then rapidly pulls the trap-line several times, thereby 

 learning that the prey is struggling in the web, runs 



•Peckham, G. W. and E. G. Sense of Sight in Spiders. Trans. 

 Wisconsin Acad. Sci., 1894. 



