No. 417.] NESTS OF AMERICAN ANTS. 707 
Polyergus goes on its cocoon-robbing expeditions unattended 
by its auxiliaries. When the colony moves to a new nest the 
Polyergus are nearly always carried by their slaves (cf. F. san- 
guinea!) In this case the slaves commonly initiate the 
change of dwelling. At home the Polyergus appear to be 
under the guardianship of their slaves and to be treated 
like helpless dependents. They are sometimes even held 
back from their sorties by the auxiliaries. 
The way in which the fertilized Polyergus queen starts her 
colony has not been observed. Forel and Wasmann have 
demonstrated that a friendly alliance may be easily effected in 
artificial nests between Polyergus queens and strange workers 
of F. fusca, and Wasmann concludes from this fact that new 
mixed colonies may be started by such consociations under 
natural conditions. But it does not appear to be necessary to 
accept this inference. The fertilized Polyergus queen may be 
quite as well able as other queen ants to raise unaided an 
incipient colony of small workers which could then pillage 
adjacent nests of fusca and provide themselves with the neces- 
sary auxiliaries. It has, moreover, been observed that Polyer- 
gus queens occasionally accompany the workers on their raids, 
and this habit may be still more pronounced in the queens of 
incipient colonies. I deem this probable because the young 
queens of other species very generally perform nearly all the 
functions which are later delegated more or less completely to 
the workers alone. 
Tomognathus sublevis Mayr (Fig. 16). — This is a small, 
rather hairy ant, with broad and edentulous mandibles. It 
occurs only in northern Europe (Finland, Sweden, and Den- 
mark). Two very careful studies of its habits have been pub- 
lished by Adlerz (86 and '96). The auxiliaries are furnished 
by Leptothorax acervorum or L. muscorum, more rarely by 
L. tuberum. | Adlerz's observations show that the Tomognathus 
Secure these auxiliaries by attacking a Leptothorax colony, 
driving away the ants, and taking possession of the nest, 
together with the larvae. The latter are then reared as help- 
mates, It is probable, however, that the T omognathus may 
occasionally recruit the number of their slaves by making 
