The neuter females are incapable of coupling; provided with reduced genital organs, they can reproduce, in certain cases, hut then lay male eggs exclusively.

Although disputed by Perez., this 'phenomenon, has for a long time been known with the honeybee ; and in fact was pointed out by Aristotle. All bee-keepers know that hives deprived of their queen are filled with males or false drones (ruches hour donneuses y-buzzing hives), and Marchai (1904) when experimenting with colonies of this kind has shown that males are produced by workers. Should not this exceptional phenomenon be attributed to the absorption by the workers of food intended for the larvae Î This was at first Marchai ?s opinion, and becomes the expression of the truth following the researches made by the distinguished biologist with the German wasp (Vespa germanica).1 It appears, in fact, from these researches that the recently issued worker wasps become egg-layers when the cells of the nest are emptied and especially when they are deprived of the queen. Then, says Marchai, "the workers, no longer having a young brood to nourish, consume the liquids which they would have given to the larvae," which induces the development of their ovaries and gives them fertility. So that the normal sterility of the workers is due to a reduced feeding, which the author justly calls "a nutritial castration."

1 P. Marchai, La reproduction et révolution des Guêpes sociales, Archives de Zool., 1896. Exp. (3), v. iv. pp. 1-100, (1896).

It is to a cause of the same 'kind, to a "food castration," that Emery (1895) attributes the production of neuters with the ants. We know, as a matter of fact, according to Forel,1 that worker ants may become fertile, and according to Eeichen-bach (1902) this fertility may be induced by suppressing their queen. Wasmann (1895) also explains by the alimentary regimen the polymorphism which he has observed in colonies of Leptothorax acervorum, and without doubt it is necessary to attribute to the same cause the multiple intermediaries which Holliday (1903) has noticed between the winged queen and the wingless individuals in Leptothorax emersoni. But it does not seem too much to admit that the workers, slightly different from the females, are capable of coupling, which would explain the experiments of Reichenbach and of Wheeler (1909), who have obtained males and workers in orphan formicaries. But the phenomenon must be infrequent, for from the eggs coming from workers Forel, Vieh-meyer, Wasmann, and Fielde always obtained males only.

So, just as bees in their hives obtain queen larvae at will by feeding the very young worker larvae with the royal jelly, the workers of social Hymenoptera may become fertile by feeding on the food intended for the brood, and in all cases, except perhaps with the ants, the fecund workers lay exclusively male eggs.

1 A. Forel, Les Fourmis de la Suisse, 1874. (Soc. helvet. des Sci. Nat. Nouv. Mém. 26).