18 
Psyche 
[March 
The present writer (Wilson 1953) has shown that all 
stages of polymorphism in ants can be explained on the 
basis of simple or modified adult allometry and correlated 
changes in the frequency distribution of size. The greater 
part of the differential growth underlying this allometry 
must occur no sooner than the prepupal stage, when 
the gross adult form is laid down by the proliferation 
and deployment of the pupal hypodermis. Certain finer 
details of allometry may not become apparent until later 
at the onset of adult development. The allometric character 
of the castes is obscured in the case of complete dimorphism, 
or queen-worker and major-minor segregation, in which 
the intermediates drop out and the log-log allometric re- 
gression curves of the two castes become disaligned. Di- 
morphism can be explained simply on the basis of abrupt 
changes in the specific growth rates of the imaginal discs 
of various organs at critical sizes or under certain physio- 
logical influences, a phenomenon which has been demon- 
strated to be fundamental in the ontogenetic growth of 
many other groups of animals (Teissier 1934, Yasumatsu 
1946). Queen-worker divergence, preceding in ontogeny 
the allometric differentiation of the worker subcastes, prob- 
ably is initiated at a critical time by the fixing in the 
imaginal discs of one of two alternative specific-growth-rate 
potentials ; this is attended by an approximate regulation of 
the course of larval development. A second threshold of 
this type may be introduced at a later stage of larval 
development in the case of major-minor dimorphism. As 
stated previously, the important specific-growth-rate po- 
tentials are completely expressed only at or after the onset 
of pupal development prior to the last larval ecdysis. This 
means that differentiation of female castes at all levels is 
probably a function of size, whether in the attainment of a 
threshold size in larval development, in the case of di- 
morphism, or in the relation of gradient allometric growth 
to the total size reached at the termination of larval develop- 
ment, in the case of the more elementary stages of poly- 
morphism. 
If an attempt is made to fit Flander’s hypothesis to this 
concept, it seems to force the proposition that the nutritive 
