a 
No. 418.] NESTS OF AMERICAN ANTS. 803 
conquered exactly like Forel’s amazons of 1870, and proved 
themselves to be quite as dependent on their slaves as their 
modern descendants; and there can be no doubt, that if 
Adam had studied and described the habits of the amazons, 
his account would agree very accurately with Huber's and 
Forel’s.”” Similarly, Wasmann stresses the long-existing 
fixity of instinct in Formicoxenus and Leptothorax (p. 226). 
No issue can be taken with him on this point — but what 
phylogenist would not take it for granted? If structure 
can remain stable during æons of geological time, certainly 
instinct may also remain relatively unchanged. It is, how- 
ever, equally true — and this point seems not to have been 
considered by Wasmann — that structure may undergo little 
change as compared with instinct. In support of this state- 
ment I would include in this place a series of facts which 
may have arrested the attention of the reader in the previ- 
ous portions of this paper, vzz., the remarkable differences of 
instinct exhibited by the species of the single genus Leptothorax. 
Morphologically, this very large and widely distributed genus 
has been justly styled * homogeneous" by Forel (74, p. 339), 
since the numerous species are closely related to one another 
and often separable only on rather trivial characters. Even 
the subgenera :Dichothorax and Temnothorax are based on 
relatively slight differences. In their habits, on the other 
hand, the species of Leptothorax are singularly diverse. 
Many of the forms have no tendency to consort with ants 
of other species, but differ considerably in the stations which 
they inhabit. Some prefer to live under stones, others in 
moss, others under bark or in dead wood, and still others, 
like one of the Texan species, in cynipid galls, or, like our 
New England Z. longispinosus Rog. in worm-eaten hickory 
nuts among the dead leaves under the trees. Many species, 
however, have a pronounced penchant for entering into more 
or less intimate symbiotic relations with other Formicidze, as 
shown in the following conspectus : : 
I. The European ZL. muscorum often lives in plesiobiosis 
With Formica rufa (see pp. 519, 520). 
2. A similar tendency is undoubtedly exhibited by our 
