April 1, 1892.] 



KNOWLEDGE 



77 



the captors are entirely dependent, even in the act of 

 feeding, upon the exertions of the slaves. The Red Ant i 

 can apparently mmage as well without slaves as with i 

 them ; moreover, it does not seem to be particular about 

 the species to which its helpers belong. Mr. F. Smith, of 

 the British Museum, used to say that he had found the 

 workers of four other kinds in the nests of this slave-owner. 



The origin of slave-holding is obscure, but it seems 

 likely that it may have arisen from the capture of pupte of 

 other species in time of scarcity, to be used as food. Ants 

 in general are quite prepared to use the pupa of other 

 species for this purpose, and if on occasions of scarcity 

 other nests were plundered and more pup;e carried off than 

 were required for immediate consumption, the residue 

 would probably mature in the nest of their captors, and 

 might then begin to take on themselves the nursing 

 function, to the manifest advantage of the other party, 

 who might thus be induced to bring in more for the same 

 purpose. Summarizing what has been said above, we have 

 shown that a smaller and weaker species of Ant may be 

 associated in the same nest with a larger and more power- 

 ful one in any of three ways — as a mere companion or 

 lodger, or even perhaps pet, as a parasite, and as a slave 

 or auxiliary. 



The nature of the nest, and, in consequence, the employ- 

 ment of the workers in constructing it, varies with the 

 species. Some, such as the Wood Ant and the Formica 

 I'xsectd referred to above, construct great mounds composed 

 of bits of stick, pine needles, bents of grass, fragments of 

 fern-fronds, &c. These fragments are not in any way 

 fastened together, but simply placed carefully one upon 

 another, in such a way as to form a fairly compact mass, 

 which is firm enough to resist a good deal of pressure. A 

 large mound, of say two feet high, and ten or twelve feet 

 in circumference, must contain many thousands of twigs, 

 and when the number and the careful disposition of these 

 is realised, one can form some notion of the vast amount 

 of labour that its construction represents, all of which 

 falls to the share of the workers. For the collection of 

 the materials, the ground for large distances round the 

 nest is traversed again and again, the army of collectors 

 following certain definite tracks, which, by the trampling 

 of innumerable httle feet, in time become distinctly marked 

 roads, and from which, in order to improve them, any 

 obstacles that are not too large nor too firmly fixed are 

 intentionally removed. A suitable fragment having been 

 discovered by any. member of the collecting party, the 

 little creature seizes its prize with its jaws in such a way 

 as least to incommode its own movements on its return 

 journey, keeping it, if possible, pointing forward and raised 

 well off the ground. On arriving at the nest it places 

 its load in position, and in doing so a good deal of 

 judgment and discretion must be exercised, for the pile is 

 not simply to be an indiscriminate heap, but is to be 

 traversed through and through with tunnels and passages, 

 large enough to allow free passage to and fro for the 

 inhabitants, and regular enough to allow of pup;e being 

 laid out along them ; and openings must be left at different 

 spots on the sides of the mound to serve as entrances to 

 the nest. These also must be so arranged that they can 

 be closed at night by putting up barricades of interlacing 

 fi-agments, a duty which devolves on sentinel workers. It 

 is nothing short of marvellous that so many hundreds and 

 even thousands of indi\-idual3 should be able to act in 

 concert, and contribute piece by piece to the raising of so 

 deftly and securely constructed an edifice, without any 

 single presiding genius to lay the plans and see to their 

 execution, and it seems to point to a remarkable degree of 

 intelligence and power of adaptation on the part of the 



workers, such as to enable them to fit in and utilize to the 

 best advantage fragments of all sorts, sizes, and shapes. 

 It is also a remarkable fact that the symmetry of the nest 

 is always well preserved ; its outline is regular, and the 

 slope even on all sides, although the builders, in conse- 

 quence of their small size as compared with the nest, and 

 their position on its surface when in the act of building, 

 cannot possibly see more than a very small portion of its 

 outline as they deposit and arrange their load. 



The above-ground structure just described is not the 

 whole of the nest ; there will be tunnels below ground as 

 well, underneath the dome, and the earth from these has 

 to be removed, fragment by fragment, by the jaws of the 

 workers, and carried up above. The growth of the nest, 

 in both its divisions, must, of course, keep pace with the 

 increase of population, which involves ceaseless labours on 

 the part of the architects and builders; while damage to the 

 structure, caused by such accidents as the fall of objects 

 upon it, will call forth the energy and skill of the engineers 

 of the community to eli'ect a speedy repair of the breach. 

 We have thus seen that, in the case of such a species as the 

 Wood Ant, the collection of materials for the construction 

 of the nest involves long and frequent journeys, and no 

 inconsiderable proportion of the time of the labourers must, 

 therefore, be spent in this employment. As its popular 

 name implies, this Ant usually forms its nest in woods, 

 preferring pine plantations, for here there will be abundant 

 material strewed about the ground wherewith to form its 

 conical piles. It is found all over the country. The slave- 

 making Ant, on the other hand, though in appearance 

 very similar, prefers to excavate its galleries in banks, or 

 round the stumps of gorse, and is found chiefly in sandy 

 localities in the southern counties, especially Surrey and 

 Hampshh'e. Formica e.rscrtu, the species referred to above 

 as having such extensive colonies, forms mounds in which 

 bits of fern-fronds, ling, and grass are used. F. cuni/crem, 

 an insect very much like the Wood Ant, also makes mounds, 

 and the Rev. Farren White mentions a large one he found 

 on a sloping bank covered with fern, heather, and gorse, 

 on the margins of a stream : it was about a foot high 

 and over eighteen feet in circumference, and had seven 

 entrances. 



Our other Ants do not form mounds of this sort, but 

 chiefly excavate the soil, or the trunk of a tree. Some, 

 like F. cunicularia, mine under stones, taking advantage of 

 the protection thus afibrded. The common F. fusca, one 

 of the chief slaves of the Red Ant, dehghts in banks, 

 especially such as face the south. The margins of the 

 footpaths in our gardens often bear witness to the presence 

 of the Garden Ant (L((.s(i« niiici'), in the little heaps 

 of grains of earth which the workers have laboriously 

 brought out one by one fi'om the soil beneath ; this species 

 will, however, sometimes excavate the stumps of trees. The 

 Black Ant {L. fuliijinosm) usually fixes on the bottom of 

 an old post or the decaying stump of a tree for its abode ; 

 it excavates the wood in galleries, the walls of which 

 always become stained black in consequence of its presence. 

 The abodes of the common Yellow Ant {L. tiacm) are the 

 rounded grassy mounds, generally something under a foot 

 in height, which are so familiar in meadows and heathy 

 places. In this instance the dome is composed of earth, 

 and though this, as well as the ground beneath, is excavated 

 through and through with tunnels, the growth of the turfy 

 grass is not interfered with, and hence great firmness and 

 compactness is imparted to the nest. As the colony 

 multiplies, the dome increases in size by the transference 

 to the outside of the particles obtained from the excavations 

 of the interior, in such a way as to distribute it uni- 

 formly and not destroy the symmeh-y of shape. As the 



