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Show 42 RIO DE JANEIRO. May-June, 1832. there is a thicket below, it suddenly falls down. I may remark, that I have distinctly seen the thread from the spinners, lengthened by the will of the animal while yet stationary, 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 manreuvre: 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 W alckenaer 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 ~ypical a g.enus 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 ano.ther spider wi~h a singularly-formed web. Strong lines radmted m a vertical plane from a common centre where ' 'II: Aza.ra's Voyage, vol. i., p. 213. May-June, 1832. ARACHNID£. 43 the insect had its station . but l connected by a symmet . ' l on y two of the rays were · nca mesh w k mstead of being as I·s ll - or ; so that the net ' genera y the · ' of a wedge-shaped segm t All case, cucular, consisted constructed. en · the webs were similarly |