96 Chapter III. 



must confine our discussion to its narrowest possible 

 limits, touching chiefly on such features as are of 

 special interest for comparative psychology. 



Great as is the variety of ant nests, still, every 

 species has its peculiar architecture, differing more or 

 less from that of any other species. Many ants, e. g., 

 our small, blackish garden ants (Lasius niger) and the 

 small, yellow meadow ants (Lasius flavus) l work 

 almost exclusively in earth. Their nests are dug in 

 the ground, but above the subterranean nest they raise 

 smaller or larger domes of earth, the stalks and blades 

 of grass, that grow on the spot, serving as natural 

 pillars and beams. Other species, again, e. g., our well- 

 known hill ants (Formica rufa) 2 build so-called "ant- 

 hills," the popular type of ant nests in our northern 

 hemisphere. These ant hills may be termed mixed 

 buildings, an under-ground earth nest being combined, 

 above ground with a dome consisting of earth, pine- 

 needles, scraps of dry leaves and stalks, and other parts 

 of plants. The different ant species which build such 

 ant hills follow systems and styles peculiar to each. 

 Thus any one with a little practice is able to determine 

 at once the species of the builders. F. rufa builds 

 differently from pratensis, pratensis from exsecta, 

 exsecta from sanguinea. The universal tool which, 

 like the human hand, is fit for and skilled in a 



1 ) Both are found also in N. America; the most common yellow 

 ant there is L. aphidicola Walsh; L. niger is represented by its very 

 common N. American race L. americanus Em. 



2 ) The N. American species of the rufa group are very numerous; 

 among them the nests of F. exsectoides For. and obscuripes For. are 

 most like the European ant hills of F. rufa. An interesting descrip- 

 tion of N. American nests is contained in a paper of Father H. Mucker- 

 mann, S. J., entitled "The structure of the nests of some North Ameri- 

 can species of Formica." ("Psyche," June, 1902.) 



