42 



RIO DE JANEIRO. May — June^ 1832. 



there is a thicket below^ it suddenly falls down. I may re- 

 mark, that I have distinctly seen the thread from the spin- 

 ners, lengthened by the will of the animal while yet sta- 

 tionary, as preparatory to its fall. If the ground is clear 

 beneath, the Epeira seldom falls, but moves quickly through 

 a central passage, from one to the other side. When still 

 further disturbed, it practices a most curious manoeuvre: 

 standing in the middle, it violently jerks the web, which is 

 attached to elastic twigs, till at last the whole acquires such 

 a rapid vibratory movement, that even the outline of the 

 spider's body becomes indistinct. 



I will here just mention a gregarious Epeira found in great 

 numbers near St. Fe Bajada, the capital of one of the 

 provinces of La Plata. The spiders were of a large size, and 

 of a black colour, with ruby marks on their backs. They 

 were nearly all of one dimension, and therefore could not 

 have been a few old individuals with their families. The 

 webs were placed vertically, as is invariably the case with 

 the genus Epeira : they were separated from each other by 

 a space of about two feet, but were all attached to certain 

 common lines, which were of great length, and extended to 

 all parts of the community. In this manner the tops of 

 some large bushes were encompassed by the united nets. 

 Azara* has described a gregarious spider in Paraguay, which 

 Walckenaer thinks must be a Theridion, but probably it is 

 an Epeira, and perhaps even the same species as mine. I 

 cannot, however, recollect seeing a central nest, as large as a 

 hat, in which, during autumn when the spiders die, Azara 

 says the eggs are deposited. These gregarious habits in so 

 typical a genus as Epeira, present a singular case among 

 insects, which are so bloodthirsty and solitary, that even the 

 sexes attack each other. 



In a lofty valley of the Cordillera, near Mendoza, I found 

 another spider with a singularly-formed web. Strong lines 

 radiated in a vertical plane from a common centre, where 



* Azara's Voyage, vol. i., p. 213. 



