204 
Psyche 
[September 
sents a new condition of subaptery which had been hitherto 
unknown until described by Dr. Wheeler. 
The specimens of M. rubriceps , six in number, were 
found to contain an interesting series of intermediate 
forms between the subapterous condition represented by 
Fig. 1. Thoracic modifications in Monomorium. 
the female mentioned above and the apterous condition 
exhibited by the worker. Dr. Wheeler first noted this 
series and figured the modifications existing in the notal 
regions of the thorax. Since the pleural regions exhibit 
various equally interesting morphological modifications 
from the winged to the apterous condition, and since they 
may represent phylogenetic stages in the origin of castes, 
