Superfamily Argiopoidea 



are rendered very conspicuous by accumulations of dust, which is 

 caught and held by the hackled band of which the web is largely 

 composed. 



Under natural conditions the web is so quickly injured by in- 

 sects and obscured by dust that its plan of structure is not easily 

 seen. But this is well-shown in some made-to-order webs that 

 were built by spiders in confinement in my laboratory. Figure 

 283 is from a photograph of one of these. 



A shallow box was made, the cavity of which served as a 

 retreat for the spider. In the centre of one face of the box a 

 hole was made for the egress of the spider; and this face of the 

 box was painted black so that if a web were built upon it it would 

 make a good background for a photograph of the web. The box 

 containing an active spider was then placed under a glass bell-jar. 

 Several cages of this kind were prepared, and in every case where 

 a spider that had been uninjured, by its trip from the South, 

 was caged a web was built on the face of the cage around the 

 opening in it, although, as a rule, several days elapsed before 

 the web was begun. 



Figure 284 represents the beginning of one of these webs. 

 Additions were made to the web from time to time, but always in 

 the night, the spider never leaving its retreat during the day-time 

 except to capture an insect that had been caught in its web. 

 Flies placed in the bell-jar were caught by the spider as soon as 

 they touched the web, the spider rushing out from its retreat 

 with great rapidity, and immediately carrying its prey into the 

 interior of the box. Figure 283, which is from a photograph 

 taken seventeen days later, represents this web in its most perfect 

 condition; later the regularity of the radiating lines was destroyed 

 by the insects that were given the spider for food; the web pre- 

 senting an appearance like that shown in Fig. 282, which is 

 the usual appearance of the webs of this species built under 

 natural conditions. 



In building this web an irregular net-work of lines was made 

 about the opening of the retreat; this net-work forms the central 

 portion of the web, and is of such structure that any disturbance 

 of the web sets it in vibration. It consists chiefly of plain threads 

 which are fastened to the supporting surface by a few attachment 

 disks but are not closely applied to this surface, so that they can 

 be readily set in motion. The net-work is continued as a tube 



294 



