INTERRELATIONS OF INSECTS 273 



terranean galleries are often complex labyrinths; frequently there are 

 long underground passages extending out in all directions, sometimes, 

 to aphid-infested roots of plants or, as in the case of the leaf-cutting 

 ants of the tropics, to trees which are destined to be attacked; special 

 chambers are set apart for the storage of food and others for eggs, larvae 

 or pupae. 



Often a nest is excavated under a stone. As Forel observes, the stone 

 warms speedily under the rays of the sun, and in damp or cool weather 

 the ants are always in the highest story of the nest as soon as the sun's 

 warmth begins to penetrate the soil, while they go below as soon as the 

 sun disappears or when its heat becomes too strong. They select stones 

 that are neither too large nor too small to regulate the temperature well, 

 while other ants attain the same object by making the nest under shelter- 

 ing herbage or by making a mound with a hard cemented roof. 



The well-known ant-hills may consist simply of excavated particles 

 of soil or else, as in the huge mounds of Formica exsectoides, may contain 

 labyrinthine passages in addition to those underground. The mounds 

 of this species are elaborate structures which may last a man's lifetime 

 at least. F. exsectoides is accustomed to form new colonies in connec- 

 tion with the parent nest ; McCook found in the Alleghanies no less than 

 i, 600 nests, forming a single enormous community with hundreds of 

 millions of inhabitants, hostile to all other colonies of ants, even those 

 of the same species. This ant covers its mound with twigs, dead leaves, 

 grass and all sorts of foreign material, and is said to close the exits of the 

 nest with bits of wood at night and in rainy weather, removing them in 

 the morning or when the weather becomes favorable. 



As Forel says [translation]: "The chief feature of ant architecture, 

 in contradistinction to that of the bees and the wasps, is its irregularity 

 and want of uniformity that is to say, adaptability, or the capacity of 

 making all the surroundings and incidents subserve the purpose of at- 

 taining the greatest possible economy of space and time and the greatest 

 possible comfort. For instance, the same species will live in the Alps 

 under stones which absorb the rays of the sun; in a forest it will live in 

 warm, decayed trunks of trees; -in a rich meadow it will live in high, 

 conical mounds of earth." Some species construct peculiar pasteboard 

 nests, as Lasius fuliginosus of Europe and tropical species of Cremasto- 

 gaster; and others spin silk to fasten leaves together, as Polyrhachis of 

 India and (Ecophylla of tropical Asia and tropical Africa, the silk being 

 probably a salivary secretion, according to Forel. 



Habits in General. The habits of ants are an inexhaustible and 

 19 



