No. 419.] MACROERGATES AMONG ANTS. 883 
individuals have some means of informing their nurses that 
their appetite is unusually keen — like that of a human being 
infested with a tapeworm. If, on the other hand, the larva 
are fed with comminuted insects, they could simply of their 
own accord eat much more food than is consumed by the 
larvae of normal workers. In either case, however, the stimu- 
lus to the increased feeding that finally results in the macroér- 
gatic stature must, of course, reside in the larva aud not in the 
worker ants which supply the food. 
The ability of a small animal like the worker of Ph. commu- 
tata to nourish a parasite larger than the normal individuals 
of the host species is accounted for by the fact that the larvæ 
and adults of these social insects are so readily fed by other 
members of the colony. The infested ant therefore suffers rela- 
tively little inconvenience when compared with an animal which 
must rely entirely on its own efforts in securing food. Both 
during the larval and adult stages the macroërgate must be fed 
by the other ants, for it is extremely doubtful whether these 
heavy-bodied individuals ever leave the nest for the purpose of 
foraging. They probably remain at home: like the heavy- 
headed soldiers. 
It is not difficult to understand how the Pheidole larva 
become infested with the Mermis, since the parasite extrudes 
its eggs within the crop of the adult worker. Such eggs or the 
embryos arising from them could easily find their way into 
the gullet and mouth of the ant and be transferred thence to 
the larvæ while the latter are being licked and cleansed; or, 
in case the workers of Ph. commutata feed their larvze by 
regurgitation, the transferring of the parasite would be still 
easier and more direct. ; 
Other interesting conclusions follow from a consideration of 
the fact that all the macroérgates are structurally of the pure 
Worker type. Except in the excessive size and peculiar hyper- 
trophy of the abdomen, I can detect no morphological differ 
ences between the parasitized individuals and their diminutive 
‘ister ants. There is certainly no appreciable tenaa m 
Approach the soldier or female type of structure. From tus 
we may conclude either that the larvae must become infested with 
