702 THE AMERICAN NATURALIST. (Vor. XXXV. 
of labor. Hence the term ‘slaves’ is much less appropriate than | 
the term * helpmates ' (auxiliaries)." 
While the various forms of social symbiosis hitherto con- 
sidered may exist between ants belonging to very different 
taxonomic subfamilies, dulosis is known to occur only between 
species of the same subfamily. This rule is based on but few 
cases, for only four genera, two belonging to the Camponotinz 
and two to the Myrmicinz, vzz., Formica, Polyergus, Strongy- 
lognathus, and Tomognathus, are known to contain dulotic 
species. Still it seems obvious that such close symbiotic 
relationships as those under consideration could be entered | 
into only by species of very similar habits and phylogenetic 
derivation. 
With the exception of Strongylognathus, the above-men- 
tioned genera are all known to occur on our continent, the 
dulotic species of Formica (F. sanguinea Latr.) and Polyergus 
(P. rufescens Latr.) being represented by distinct races, or sub- 
species, the genus Tomognathus by a distinct species (7. ameri- 
canus Emery). So little attention, however, has been devoted 
to our ants, that we may yet look forward to the discovery of 
an American Strongylognathus, for there are in America sev- 
eral species of the genus Tetramorium (including the sub- 
genus Xiphomyrmex) which are allied to the Tetramorium 
cæspitum auxiliary of the European Strongylognathus. 
The meagre work which has been done on our American 
dulotic ants is barely sufficient to show that their behavior 1$ 
essentially like that of their European allies. Since these ants 
in America select their auxiliaries, or slaves, from à slightly 
different though allied ant fauna, we may yet expect to find 
some interesting differences in the details of habit and 
behavior. ; 
Before enumerating the American species, together with 
their auxiliaries, it will be convenient to present a much con- 
densed résumé of the splendid accounts of the European 
observers, Forel, Wasmann, and Adlerz. : 
Formica sanguinea Latr.— This species is a true Formic 
which is sometimes found living without auxiliaries. It has 
broad, toothed mandibles, of the type characteristic of 
