270 HABITATIONS OF INSECTS. 
But however rude its outward appearance, and the articles of which it 
consists, interiorly it presents an arrangement admirably calculated at once 
for protection against the excessive heat of the sun, and yet to retain a due 
degree of genial warmth. It is wholly composed of numerous small apart- 
ments of different sizes, communicating with each other by means of gal. 
leries, and arranged in separate stories, some very deep in the earth, others 
a considerable height above it: the former for the reception of the young 
in cold weather and at night, the latter adopted to their use in the daytime. 
In forming these, the ants mix the earth excavated from the bottom of the 
nest with the other materials of which the mount consists, and thus give 
solidity to the whole. Besides the avenues which join the apartments 
together, other galleries varying in dimensions communicate with the out- 
side of the nest at the top of the mount. These open doors would seem 
ill-caleulated for precluding the admission of wet or of nocturnal enemies : 
but the ants alter their dimensions continually according to circumstances ; 
and they wholly close them at night, when all gradually retire to the in- 
terior, and a few sentinels only are left to guard the gates. On rainy 
days, too, they keep them shut, and when the sky is cloudy open them 
partially.+ 
The habitations of these ants are much larger than those of any other 
species in this country, and sometimes as big as a small haycock ; but the 
are mere molehills when compared with the enormous mounds which other 
species, apparently of the same family, but much larger, construct in warmer 
climates. Malouet states, that in the forests of Guiana, he once saw ant- 
hills which, though his companion would not suffer him to approach nearer 
than forty paces for fear of his being devoured, seemed to him to be fifteen 
or twenty feet high, and thirty or forty in diameter at the base, assuming 
the form of a pyramid, truncated at one-third of its height?; and Stedman, 
when in Surinam, once passed ant-hills six feet high, and at least one 
hundred feet in circumference.’ In the plains of Paraguay, where the ants 
commit great devastations, a species described by Dobrizhoffer forms conical 
earthen nests three or more ells high, and as hard as stone; and in the 
Bungo forest in New South Wales, a yery small ant builds nests of indu- 
rated clay eight or ten feet high.4 
The nest of Formica brunnea is composed wholly of earth, and consists 
of a great number of stories, sometimes not fewer than forty, twenty below 
the level of the soil, and as many above, which last, following the slope of 
the ant-hill, are concentric. Each story, separately examined, exhibits 
cavities in the shape of saloons, narrower apartments, and long galleries 
which preserve the communication between both. The arched roofs of the 
most spacious rooms are supported by very thin walls, or occasionally by 
small pillars and true buttresses ; some having only one entrance from 
above, others a second communicating with the lower story. The main 
galleries, of which in some places several meet in one large saloon, com- 
municating with other subterranean passages, which are often carried to 
the distance of several feet from the hill, These insects work chiefly after 
sunset. In building their nest they employ soft clay only, scraped from its 
bottom when sufficiently moistened by a shower, which, far from injuring, 
1 Huber, Recherches sur les Meurs des Fourmis, pp. 21—29. 
2 Ibid. p. 168. 5 Stedman’s Surinam, i. 169. 
4 Westwood, Mod, Class. of Ins, ii. 223. 231, - 
