706 THE AMERICAN NATURALIST. | [Vor. XXXV. 
since the days of Pierre Huber (10, p. 210 eż seg.). They have 
been admirably described by Forel (74), who has also estimated 
(pp. 320, 321) the number of expeditions undertaken by a 
single powerful colony of these ants during a single summer. 
In thirty days (from June 29 to August 18, 1873) he witnessed 
forty-four expeditions of the amazons. These usually occurred 
between 2 and 5 o'clock P.M., the time limits being from 1.30 to 
6p.M. Among the forty-four expeditions there were forty-one 
attacks, nineteen on fusca and nineteen on rufibarbis, and three 
of which only the return was observed. The total number of 
cocoons robbed was estimated at 29,300 (14,000 fusca, 13,000 
rufibarbis, and 2300 of unknown origin but probably fusca). 
Counting in the expeditions after August 18, which he was 
unable to witness, Forel concludes that not far from 40,000 
larvae and pupa of the auxiliary species were appropriated 
during the summer of 1873 by a single Polyergus colony ! Most 
of the pupze were consumed, so that few of them ever hatched 
and became auxiliaries. And although two species were pillaged 
the colony later became almost entirely F. fusca. 
Wasmann (91, pp. 61, 62) has observed that the fusca auxilia- 
ries are noticeably: fiercer and more courageous than when 
nesting alone. The same is true of fusca in sanguinea nests. 
This is explained by Wasmann as merely a special case of the 
general rule that all ants are more courageous when they feel 
themselves backed by numbers. 
The shadow side of the life of Polyergus is seen within its 
nest, where it is abjectly dependent on its slaves. Here e: 
spends most of its time preening its legs and antennz, as it is 
quite unable to excavate. On this account the character of 
the nest architecture is entirely determined by the auxiliary 
species. Moreover, the conformation of its mandibles is such 
that Polyergus cannot care for its own young or the pup® of 
its slaves, though it sometimes licks the newborn callows. 
fter a minute investigation of the question as to whether 
Polyergus is able to feed itself, Wasmann concludes that it can 
lap up liquids but is usually fed by the slaves. This mode of 
obtaining its food is, in fact, so essential, that it dies of starva- 
tion when deprived of its helpmates. 
