POLYMORPHISM. 121 



pletely established, however, in certain genera and species with the 

 suppression of the desmergates. A remarkable example of division 

 of labor, without corresponding structural differentiation, is seen also 

 in the CEcopliylla above mentioned, an ant which inhabits nests of 

 leaves sewn together with fine silk. According to the observations of 

 Dock! (1902) and Dorlein (1905), when the nests are torn apart the 

 monomorphic workers separate into two companies, one of which 

 stations itself on the outside of the nest, draws the separated leaves 

 together and holds them in place with the claws and mandibles, while 

 the other moves the spinning larvae back and forth within the nest till 

 the rent is repaired with silken tissue (see p. 2i< ). 



3. An interesting case is presented by the honey-ants (Myrmecocys- 

 tns iiiclligcr and inc.ricaints ). All the workers of these species, though 

 variable in size, are structurally alike. Among the callows, however. 

 and quite independently of their stature, certain individuals take to 

 storing liquid food, as I have found in my artificial nests of the latter 

 species, and gradually, in the course of a month or six weeks, become 

 repletes, or plerergates. Except for this physiological peculiarity, 

 which gradually takes on a morphological expression, the plerergates 

 and ordinary workers are indistinguishable. \Ye must assume, there- 

 fore, that the desire to store food represents an instinct specialization 

 peculiar to a portion of the callow w'orkers. There can be no doubt 

 that as our knowledge of the habits of ants progresses many other 

 cases like the foregoing will be brought to light. 



It may be maintained that in these cases physiological states must 

 precede the manifestation of the instincts, and that these states, how- 

 ever inscrutable they may be, are to be conceived as structural differen- 

 tiations. There is undoubtedly much to justify this point of view. 

 The elaborate sequence of instincts in the queen ant, for example, is 

 accompanied by a series of physiological changes so profound as to be 

 macroscopical. After the loss of her wings, the wing muscles degen- 

 erate and the fat-body melts away to furnish nourishment for the 

 ovaries, which in the old queen become enormously distended with 

 eggs as the breeding season approaches. Such changes would seem 

 to be amply sufficient to account for the changing instincts. I have 

 found that mere artificial deflation at once alters the instincts of the 

 queen, probably through a stimulus analogous to that which leads to 

 the atrophy of a muscle when its nerve is severed, and in the case 

 under consideration leads to the degeneration of the wing-muscles and 

 to changes in the ovaries. In the mermithergates and pseuclogynes we 

 also have peculiarities of behavior which are attributable to peculiar 



