HORIZONTAL SNARES AND DOMED ORBS. 



169 



horizontal one; and that it is lifted up gradually by attaching lines at 

 various points upon the upper surface and drawing them taut, one after 

 another, until the whole is lifted up into the domed structure represented 

 in Fig. 154. I may add that Dr. Marx was also able to collect cocoons of 

 the species, and describe the manner in which they are liung in the neigh- 

 borhood of the web.^ 



The manner in which this change is wrought was determined by Dr. 

 Marx, and he has kindly placed at my disposal his notes upon the same. 

 When first observed by him (at 8.30 A. M.), the snare lay in a horizontal 

 plane, as shown at Fig. 158, and had more than fifty radii. It was hung 

 between the tips of the branches of a bush. At 12 M. the borders of the 

 snare were bent downward, causing it to assume the form of a shallow 

 dome. At 4 P. M. the transformation hud so far progressed as to bring the 

 web to the structure represented at Fig. 159. The work was carried on in 

 this wise : At the marginal edges were 



outgoing lines, as c b, Fig. 



158, used to support 



or brace the snare, as 



is usual with hor- 



T izontal orbs. On 



Fig. 158. 



Basilica spider's mode of transforming a horizontal 

 into a domed orb. 



assumed the po- 

 the depression of 

 of the outside or 



these at certain points (c) w^ere fastened lines (c d), 

 which were attached to a branch (d) some distance 

 below and to one side of the plane. These lines 

 (c d) were gradually borne downward until they 

 sit ion of the dotted line, a b. This action caused 

 the edges ; and by continuing this manipulation 

 foundation lines, the orb was forced first into the shajje of a shallow dome 

 flattened at the pole, and then into the form of the typical web as above 

 described. (Fig. 159.) This action was seen "repeated over a dozen times." 

 But it was manifest that some other method had been brought to bear 

 than that already explained. The position of the snare in its original 

 horizontal form had been exactly located by a fork (f, Fig. 158), in the 

 branch to which the stay lines were attached, which was on a level with 

 the horizontal axis of the orb. Now, however, the edges of the web were 

 not only drawn below the level of the fork, but the central part was raised 

 at least three-fourths of an inch above the fork. (Compare f. Fig. 158, 

 with f. Fig. 159.) The manner in which this had been done was readily 

 seen by a glance at the various lines, perpendicular and inclined, which 



' See Vol. II., Chapter on Maternal Industrj', 



