INTERRELATIONS OF INSECTS 2QI 



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 tem- 

 perature well, while other ants attain the same object by making the 

 nest under sheltering 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 

 e 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 

 ever-fascinating subject of study to the naturalist, and well repay the 

 most critical observation. While each species has its characteristic 

 habits, ants in general have many customs in common. 



Thus ants of one colony exhibit, as a rule, a pronounced hostility 

 toward ants of any other colony, even one of the same species, but 



