on their backs,
having gregarious habits. 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 Walckanaer thinks must be a
Theridion, but probably it is an Epeira, and perhaps even the same
species with mine. (2/10. Azara's "Voyage" volume 1 page 213.) 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. As all the spiders which I saw were of the same
size, they must have been nearly of the same age. 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. In our passage to the Plata, we saw
nothing particular, excepting on one day a great shoal of
porpoises, many hundreds in number. The whole sea was in places
furrowed by them; and a most extraordinary spectacle was presented,
as hundreds, proceeding together by jumps, in which their whole
bodies were exposed, thus cut the water. When the ship was running
nine knots an hour, these animals could cross and recross the bows
with the greatest ease, and t