114 
ZOOLOGY: W. M. WHEELER 
workers, without distinct mesonotal and metanotal sclerites and with- 
out ocelli. The first specimen is therefore of the subapterous meso- 
notal type, the second is apterous and stenonotal, the third and fourth 
are ergatogynes. Thus the three species, M. rothsteini, subapterum 
and rubriceps together represent all the principal stages from the per- 
fect female to the worker. 
My study of the large genus Monomorium shows that in some species 
the only females are stenonotal and apterous {M. floricola, carbonarium, 
etc.), whereas in others they are ergatogynes (M. venustum, schurri, 
etc.). In still other species both winged and ergatogynic forms occur 
(lece, dichroum, etc.). This "morphological restlessness" of the female 
is evidently a survival of a condition which was once common' to all 
ants but which has disappeared in most genera through a survival of 
the two extremes of the graduated series of forms, the macronotal, 
winged form (female proper) and the micronotal, apterous form (work- 
er), and the suppression of all the intermediate phases. That the 
species of Monomorium should retain so complete a picture of the various 
stages that have led up to the development of the worker caste is not 
surprising when we stop to consider that the genus is one of the most 
primitive in the subfamily Myrmicinae. This is shown by its simple 
morphological characters, the present cosmopoKtan distribution of its 
species, their dominance in the ant-faunas of regions noted for the archaic 
character of their biota (Africa, Southern Asia, Australia and New 
Zealand), and the known geological age of the genus, which is repre- 
sented in the Baltic amber by two species differing but sHghtly from 
existing forms. Space forbids a discussion of a few other Formicid 
genera in which a similar diversity of females is known to occur. Among 
the ants as a family we may conveniently recognize the following female 
types which at the same time represent stages in the phylogenetic de- 
velopment of the worker: 
1. The macronotal, winged female. — Most ants. 
2. The mesonotal, subapterous female. — Monomorium subapterum 
and rubriceps var. cinctum. 
3. The stenonotal apterous female. — Some species of Monomorium ^ 
Anochetus, Myrmecia, Odontomachus hastatus, etc. 
4. The micronotal female, or ergatogyne. — Some species of Mono- 
morium and Crematogaster, Polyergus refescens. 
5. The ergatoid female. — Leptogenys, Acanthostichus, Sphinctomyr- 
mex, Onychomyrmex, Paranomopone. These forms grade into the 
'dichthadiigynes' of the Dorylinae. 
