May, 1920] Studies in Food of Spiders 245 



that at that time most of the webs are made by mature spiders. 

 The stabihmentum. is constructed in the young stages of this 

 spider because the web is smaller and needs more support when 

 a large insect gets entangled in it. 



No trapline is made but she hangs head downward in the 

 center of the hub. When a very large insect becomes entangled 

 in the web this spider often makes a hasty retreat. Sometimes 

 it drops to the ground and remains perfectly still until the 

 danger is past then it goes back to the dragline it spun while 

 descending and assumes its former position on the hub of the 

 web. At other times especially when the web is made in big 

 weeds or small bushes, it ascends the web and lies very still on 

 top of a leaf for sometime when it again returns to its former 

 position. Like Argiope riparia, this spider makes barrier 

 webs on each side of the main web. Sometimes the barrier 

 web is made on only one side of the web. These barrier webs 

 are more loosely constructed than is the main one. Although 

 I have no definite explanation for the barrier webs, I think 

 they are constructed for keeping out very large insects. Often 

 when an insect strikes the web of Argiope trifasciata the spider 

 begins to swing the web until it vibrates very rapidly. I 

 think this is done for two purposes. If the insect is a large 

 •one the spider can entangle it sufficiently so that it can wrap it 

 up in a swath of silk when it once advances on it. But if the 

 insect is so large that it is beyond the spider's control, the 

 insect may flounder in the web and becomes entangled without 

 any more serious damage than destroying the spider's home 

 which can soon be reconstructed. 



This habit varies greatly with different individuals of this 

 species and sometimes it seemed to me they were trying to 

 shake the insect out of the web. Sometimes this spider 

 advances on a large grasshopper without an attempt at vibrating 

 the web. Many times the victim was twice the size of the 

 .spider and was so quickly swathed in a white band of silk that 

 the eye could scarcely register the movements and it was with 

 difficulty that the web was pulled off the victim. It may be 

 that this is a sign of fright as I have made them vibrate the web 

 violently by merely approaching the web or casting something 

 into it, but I hardly think this is a good explanation. When an 

 insect flies into the web the spider rushes on it from its position 

 on the center of the hub and sometimes pierces it with the 



