On Flanders' Hypothesis of Caste Determination in Ants

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 terebra.nt Hymenoptera. The degree of ovisorption in turn is assumed to be a function of one or more environmental 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 evi.dent that any tr.ophic influence on caste formation must be made effective through an agency common to all ant col,onies. Such an agency is most likely to consist of a set of conditions resident in the queen. Morphological differentiation would be initiated therefore prior to egg deposition." Dr. llanders has recently published the paper read at the l:)ecember 1952 meeting of the American Section of the International Union for the Study of Social Insects (Scientific Monthly, 76: 142-148, 1953). This contains an extensive elaboration of his hypothesis, w;h heavy emphasis on examples drawn from the terebran Hymenoptera, but presents no new experimental evidence bearing on ants nd does not take in,o account the objections raised by myself at the original read-