This gregarious habit, in so typical a genus as Epeira, among insects, which are so bloodthirsty and solitary that even the two sexes attack each other, is a very singular fact.
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 the insect had its station; but only two of the rays were connected by a symmetrical mesh-work; so that the net, instead of being, as is generally the case, circular, consisted of a wedge-shaped segment.

All the webs were similarly constructed.
(PLATE 14.

DARWIN'S PAPILIO FERONIA, 1833, NOW CALLED AGERONIA FERONIA, 1889.) CHAPTER III.
(PLATE 15.

HYDROCHAERUS CAPYBARA OR WATER-HOG.) Monte Video.
Maldonado.
Excursion to R.Polanco.
Lazo and Bolas.
Partridges.
Absence of Trees.
Deer.
Capybara, or River Hog.
Tucutuco.
Molothrus, cuckoo-like habits.
Tyrant-flycatcher.
Mocking-bird.
Carrion Hawks.
Tubes formed by Lightning.
House struck.
MALDONADO.
JULY 5, 1832.
In the morning we got under way, and stood out of the splendid harbour of Rio de Janeiro.