68 Annals Entomological Society of America [Vol. I, 



trances. In other genera, like Camponotus, Atta, Pheidole, etc., 

 with species that have desmergates, the morphological differen- 

 tiation between foragers and guardians is still unsettled. It 

 becomes completely established, however, in certain genera and 

 species w4th the suppression of the desmergates. A remarkable 

 example of division of labor without corresponding structural 

 differentiation is seen also in the above mentioned CEcophylla, an 

 ant which inhabits a nest of leaves sewn together with fine silk. 

 According to the observations of Dodd (1902) and Doflein (1905), 

 when the nest is torn apart the monomorphic workers separate 

 into two companies, one of which stations itself on the outside, 

 draws the separated leaves together and holds them in place 

 with the claws and mandibles, while the other moves the 

 spinning larv« back and forth within the nest till the rent is re- 

 paired with silken tissue. 



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

 mecocystus melliger and mexicanus.) All the workers of these 

 species, though variable in size, are structurally alike. Among 

 the callows, how^ever, 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 slowly takes on a mor- 

 phological expression, the plerergates and ordinary" workers are 

 indistinguishable. We must assume, therefore, that the desire to 

 store food represents an instinct specialization peculiar to a 

 portion of the callow workers. 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, however inscrutable they may be, are to be conceived as 

 structural differentiations. There is undoubtedly much to jus- 

 tify this point of view. The elaborate sequence of instincts in the 

 queen ant, for example, is accompanied by a series of physiologi- 

 cal changes so profound as to be macroscopical. After the loss of 

 her wings, the wing muscles degenerate 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 chans:ing instincts. I have found 



