June, (902] 



PSYCHE. 



359 



calling them " mounds," at least as a gen- 

 eral thing. But far different is the case 

 with regard to the inner struct ure, which, 

 ceteris paribus, is much more consider- 

 able. Wasmann defines a formicary as 

 an " irregular aggregation of chambers 

 and tunnels serving as the abode of ants 

 and their brood and connected by differ- 

 ent apertures with the outside world."* 

 To characterize our ant-nests the follow- 

 ing qualifications might be added to the 

 above definition. In the first place, 

 American nests descend to a relatively 

 great depth. The part covered by frag- 

 ments of woody material is but a small 

 fraction of the dome. It is only in the 

 case of F. ohscuripes, that now and then 

 not only the dome but also a considerable 

 part of the nest itself consists of the 

 above mentioned material. Below the 

 dome the nest assumes gradually larger 

 dimensions, until at a depth of 1.50 m. 

 it often reaches a diameter of 2 m. and 

 beyond. In a nest of F. rubicunda I 

 found a few days before the first vernal 

 oviposition ants in considerable numbers 

 only at the depth of i m., a queen only 

 at 1.25 m.t I had to penetrate to a 

 like depth in the case of F. exscctoidcs 

 and others. I examined one nest of F. 

 exsectoides during November, when the 

 ants had already retired to their winter 

 quarters. Several hours were consumed 

 in digging. After having reached a 



* E. Wasmann, S. J. Vergleichende Studien ueber das, 

 Seelenleben der Ameisen und der hoeheren Tiere. 2. Aufl. 

 p. 67. 



tOf course during the lime of oviposilion 9 s and 5 s 

 may be found directly below the nest's surface. 



depth of 2 ni., I decided to desist. 

 Most of the ants were found singly. 

 Many were lying with their legs ex- 

 tended and embedded in the cold earth. 

 It was only in the tunnels, which often 

 follow the course of the roots, that we 

 found clumps of ants as they are to be 

 seen during winter in observation nests. 

 One queen alone was captured ; and yet it 

 is well known that queens of F. exsectoides 

 abound. Since we were concerned with 

 a very populous nest, the principal part 

 of it was necessarily still deeper down. 

 Another peculiarity is to be found in the 

 tunnels. Towards the surface they are 

 highly concentrated ; soon they separate 

 further and further and being now hori- 

 zontal now vertical, they penetrate into 

 all parts of the nest. In the nest just 

 mentioned, as also in some others, there 

 were found at the depth of 1.50 m. di- 

 rectly below the dome only four irregu- 

 lar tunnels within a square meter. 



A third characteristic feature, finally, 

 is the preference manifested by the ants 

 for stony locations. It is true that this 

 is owing more to the character of the 

 soil. But in virtue of their well devel- 

 oped faculty of adaptation, which is only 

 a manifestation of their plastic instinct, 

 these ants have been enabled to utilize 

 this circumstance in an appropriate man- 

 ner. For, the stones not only mean a 

 great saving of work for the ants, but 

 also impart great solidity to their struc- 

 tures. Moreover, they facilitate the reg- 

 ulation of temperature during spring, 

 and in winter and summer such a rocky 

 abode affords the best protection against 



