No. 415.] NESTS OF AMERICAN ANTS. 535 
have overlooked these ants on several former occasions. They 
had evidently been feeding on the dead Camponotus and were 
moving in and out of their tenuous galleries excavated below 
the refuse heap in the compact black soil. On digging I dis- 
covered the singular soldier (2.5 mm. long, Fig. 11 a), which is 
unlike the soldier of any other Pheidole known to me except 
Ph. absurda Forel from tropical America.  Forel's species, 
however, is larger and exhibits several other differences. 
The soldier of P4. lamia is smooth and of the same honey- 
yellow color as the worker, except for the rough, brownish, 
Colobopsis-like anterior portion of its head. The abdomen of 
both soldier and worker has in its center a large dark spot, 
which is produced by the black contents of the stomach seen 
through the thin integument. The visual organs in both 
castes have undergone the usual reduction noticeable in hypo- 
gæic ants — there being scarcely more than a dozen facets in 
each of the small, emarginate eyes of the soldier.! 
IV. XENOBIOSIS. 
The inquilines, or guest ants (Gastameisen), constitute a group 
of considerable interest, since it is not improbable that these 
insects may ultimately give us some clue to the conditions that 
have led to the development of mixed nests from those of the 
double or compound variety. Unfortunately we know very 
little of the habits of some of the species that have been 
recorded as guest ants. So far as known the inquilines main- 
tain their independent households, although they consort freely 
with their hosts and live with them on terms of mutual tolera- 
tion, or even friendship. The best-known guest ant is the 
- There—after the fashion of Solenopsis molesta—it occupies a sm 1 
Chamber of its own, which connects with the galleries of the larger ants. These 
Peacefully tolerate and scarcely notice their tiny neighbors.” 
