64 
Psyche 
[March 
pseudogyne is characterized by an enlarged mesonotum and 
oftentimes by the presence of vestigial wings. It is more 
robust than the worker, and in the case of some forms re- 
tains the median ocellus which entirely disappears in the 
worker. However, a very complete series of intergrades 
may be noted, and in some cases a pseudogyne so nearly 
approximates a worker in size and in shape that a careful 
examination is necessary to differentiate between them. 
Pterergates and pseudogynes are easily distinguishable. In 
the case of a wingless pseudogyne and a pterergate, the dis- 
tinction is obvious. In the case of a winged pseudogyne 
and a pterergate, the difference is one of size and structure 
of the thorax. Usually in winged pseudogynes the lower 
intergrades tend to lose their wings as they become re- 
duced in size, so that the less developed individuals differ 
only in size from the worker and from the pterergates both 
in size and the absence of wings. 
From the foregoing discussion of the polymorphic forms 
of the female ant, it may be noted that the distinctions be- 
tween the forms are based mainly upon thoracic characters. 
The thorax of the female ants is as specialized as any that 
may be found among the winged insects, while the thorax 
of the worker ants is the most highly specialized, and at the 
same time as simplified as may be found among all insects. 
Adlerz has stated in his Myrmecologiska Studier that “we 
know that those characteristics that distinguish the typical 
worker from the queen are partly of a retrogressive nature ; 
for example, the reduction of the receptaculum seminis, 
ovaries, eyes, wings, together with their muscles and mus- 
cular attachments, and partly progressive, for example, the 
increased size of mandibles and their muscles.” The adop- 
tion of a terrestrial habit and the subsequent disappear- 
ance of wings has resulted in a fusion of sclerites in the 
thoracic region which makes a homological study almost 
impossible. Usually the dimorphic forms, the winged sexual 
forms and the wingless workers, are the only forms avail- 
able for study, the intermediate forms having disappeared 
during phylogeny. Occasionally intermediate forms appear, 
giving convenient graduations from the winged to the wing- 
less state, showing how the fusion of the sclerites and the 
simplification of the thorax may have taken place. In the 
