ON FLANDERS’ HYPOTHESIS OF CASTE 
DETERMINATION IN ANTS* 
By Edward 0. Wilson 
Biological Laboratories, Harvard University 
S. E. Flanders (1945, 1952) has recently advanced a 
hypothesis concerning caste determination in ants which 
has gained wide recognition. According to Flanders, the 
nutritive material available to the female embryo in the 
egg determines the developmental path it will follow as a 
larva, producing finally a queen or one of the worker 
subcastes. The available nutritive material is assumed to 
be a function of the degree of ovisorption, since this has 
been shown to be the basis of discontinuous variation in 
several terebrant Hymenoptera. The degree of ovisorption 
in turn is assumed to be a function of one or more environ- 
mental influences affecting the queen. One of the ways the 
environment can act is through its effect on the rate of 
oviposition, which is probably inversely related to the 
degree of ovisorption. 
What appears to be the crux of Flanders’ hypothesis is 
stated as follows in his 1952 paper: “Since the worker 
caste is characteristic of all non-parasitic ants, irrespective 
of the wide variation in the larval nutrition of the various 
species, it is evident that any trophic influence on caste 
formation must be made effective through an agency com- 
mon to all ant colonies. Such an agency is most likely to 
consist of a set of conditions resident in the queen. Morph- 
ological differentiation would be initiated therefore prior 
to egg deposition.” 
* Dr. Flanders has recently published the paper read at the December 
1952 meeting of the American Section of the Internaitional Union for 
the Study of Social Insects (Scientific Monthly, 76: 142-148, 1953). 
This contains an extensive elaboration of his hypothesis, wifih heavy 
emphasis on examples drawn from the terebrant Hymenoptera, but 
presents no new experimental evidence bearing on ants and does not 
take into account the objections raised by myself at the original read- 
ing and presented once again in the following paper. 
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