IOIO THE AMERICAN NATURALIST. [VOL. XXXV. 
placed in the nest. During the morning hours they were 
killed by the Pachycondyla workers, shorn of their many legs, 
cut up into pieces of convenient length, malaxated, and fed to 
the larva as on the preceding day. And again I was able to 
witness the strange banquet — the dwarf reaching down from 
the shoulders of the-ogre and helping himself from the charger 
formed by the trough-like belly of his host. The same obser- 
vation was repeated on several successive days. Pieces of 
various ant-larvae, beetle-larvee, Lithobius, Scutigera, Oniscus, 
— all were served up to the ant-larve and partaken of with 
great relish by the dipteron larvae as well. There could be no 
doubt that the latter were true commensals, — perhaps the 
most perfect commensals, in the original meaning of the term, 
to be found in the whole animal kingdom ! 
As one of the smallest Pachycondyla larva, scarcely one- 
fourth grown, bore a very small dipteron larva, it is, perhaps, 
safe to say that the ant-larva acquires its commensal at a very 
early age. The two then grow up together, so that there is 
always a certain relation between the two kinds of larvae — 
large Pachycondyla larva bearing large commensals, and vice 
versa. The worker ants lick and cleanse the commensals at 
the same time that they are caring for their own larva. This 
is usually done just after meals. Since, during this operation 
of cleansing, the ants spend no more time over the commensals 
than they do on a similar area of the body surface of their own 
larvae, it would seem that they are not even aware of the exist- 
ence of the commensals. To these nearly blind ants, which 
must rely almost exclusively on their senses of touch and smell, 
the larvae bearing commensals, if distinguished at all from indi- 
viduals without such attendants, would probably be perceived 
merely as having unusually protruding necks. But there is 
nothing to indicate that these insects are really capable of per- 
ceiving such differences in their environment. 
At this time an amusing interlude in these observations was 
furnished by introducing into the nest a few living * pill-bugs " 
(Armadillidium sp.). For two whole days the Pachycondyla 
workers hunted these isopods from one corner of the nest to 
another. An Armadillidium would scurry along rather quickly 
