OHAPTEE XIV. 



MECHANICAL STRENGTH OF WEBS AND PHYSICAL POWER 



OF SPIDERS. 



I. 



THE size of orbwebs varies generally with the size of the builders. But 

 location, the condition of the wind, and contiguity of other webs have 

 much to do in determining the matter. 



The abundance of insect food may be a factor modifying both form 



and size. An example of this was seen 



in the colony of Epeiroids referred to, 



Chapter III., as stretching their 



Food ne j. g across the water between the 



??,7 boat houses at Atlantic City. 

 Moaines. 



(Fig. 61.) There the flies swarmed 

 in such myriads that the difficulty of ob- 

 taining food was reduced almost to the 

 minimum. As a consequence most of the 

 spiders hung in the merest rudiments of 

 webs, as shown at Fig. 216. In some cases 

 these may have been the remains of more 

 or less perfect snares, which had become 

 reduced to remnants by struggles of in- 

 sects; but many of them showed no traces of any other architecture than 

 that here represented, and I inferred that the spiders had discovered that 

 the building of complete orbs was a useless waste of labor and material, 

 and had spun no more than the central space. 



A Furrow spider taken from the railings of a bridge, where its space 

 was circumscribed by location and by numerous webs of its fellows, when 

 placed in a roomy cell spun an orb eleven and a half inches 

 long by eight inches wide, hung upon a foundation line sixteen 

 inches long. The same aranead, when placed in a glass jar three 

 inches wide, wove a small characteristic web, or an apology for one, not 

 unlike the rudimentary snare at Fig. 216. Argiope cophinaria often makes 

 a very small web, and is quite sure to do so when the arboreal spaces 

 surrounding it are straitened. But when domiciled where her lines 

 could be carried long distances I have known her to make an orb more 

 than two feet in diameter. 



(229) 



.FiG. 216. A rudimentary snare of Epeira. 



Modified 

 by Site. 



