No. 415.] NESTS OF AMERICAN ANTS. 537 
by Adlerz (84). Its colonies, usually consisting of a small 
number of individuals, may, however, be very populous at 
times. It establishes its nest in the very interior of the nest 
of Formica rufa or of F. pratensis. The small chambers which 
it there constructs and inhabits, together with its progeny, 
communicate by means of large openings with the galleries of 
the Formica nest. Wasmann (91, p. 35) found a colony of 
Formicoxenus consisting of workers, males, queens, and young, 
inhabiting the cavity of an old cocoon of Cetonia Jforicola, a 
beetle which lives during its larval stages in the bottom of the 
nest of Formica rufa. Formicoxenus nitidulus often moves 
about among its hosts. The observations of Adlerz, Forel, 
Wasmann, and myself prove that these myrmecophiles are 
never met with outside of the nests of the Formica rufa and 
F. pratensis. They live in peace with their hosts, but they are 
not cared for by them, nor do they render them any service. 
Observers who have studied the behavior of this species have 
on exceptional occasions observed acts of a slightly hostile 
nature on the part of the two species, but these acts were 
without serious consequences. On one occasion, in one of my 
artificial nests, in which the ants had previously lived on good 
terms with one another, I saw a Formica touching a Formi- 
Coxenus with her antennz and menacing her with her mandi- 
bles ; but she departed without even attempting to seize the 
inquiline. In the same nest I found a Formicoxenus which 
had seized the leg of a Formica in its mandibles and had died 
in this position. The Formicoxenus (Forel, '86, p. 134) are 
able, either by themselves or by carrying one another, to 
follow the files of their hosts when the latter move into a new 
nest. They also carry their progeny to the new nest. In the 
nests of their hosts they find shelter, warmth, and efficient 
protection from other ants, against which they would be unable 
to defend themselves. There they also find sustenance, but it 
has been impossible up to the present time to determine its 
nature,” 1 
a ‘In Emery’s Beiträge ('95, pp. 271, 272), F. nitidulus is cited as occurring in 
North America. The specimens to which Emery refers were labeled * Rocky 
Mountains". But Emery (zn Zifteris) has expressed grave doubts concerning the 
