800 THE AMERICAN NATURALIST. (VoL. XXXV. 
of synclerobiosis (especially those of /. exsectoides with sub- 
sericea) are due to a sporadic outcropping of this ancient 
instinct. In view of the further facts that sanguinea can get 
on perfectly without auxiliaries, that it is the young colonies 
which usually contain the greatest number of slaves, and that 
the number of these is often highly variable in different colo- 
nies even in the same localities, we are certainly justified in 
demanding more stringent proof that sanguinea really robs for 
the sake of rearing slaves? Laying most stress on the fact that 
the booty serves as food, — and of this Forel's observations 
contain sufficient evidence (74, p. 258)? — we may regard the 
imaginal auxiliaries in the sanguinea nests as a mere by-product, 
as it were, of the colonial activities. The sanguinea often 
appropriate more food than they can devour, and the residuum 
merely adds workers to the colony, which are not harmful and 
may even be advantageous. This is evidently the interpreta- 
tion intended by Darwin, who does not pretend to invoke the 
principle of natural selection in his genetic explanation of 
the sanguinea stage of dulosis, so that Wasmann has taken 
unnecessary pains to refute an imaginary argument. With 
should hatch, the nomadic habits of the Ecitons and their poorly developed 
deportation instinct would prevent the formation of permanent mixed colonies 
since the larvae and pupae which they kidnap belong to home-loving spect 
1 At Colebrook, Conn., I recently found three cases of synclerobiosis in 1 addi- 
tion to those enumerated in the second part of this paper: (1) acolony of F. exsec- 
toides with F. subsericea, similar to the mixed colonies of these species observ: 
by Forel and Schmitt; (2) F. nitidiventris with F. rufa var. obscuripes Forel ; 
(3) Z. nitidiventris with F. rufa var. difficilis Emery. All of these colonies were 
small, and in none of ihn could I find the queens of either of the consociating 
species. 
? Wasmann believes (91, p. 198) that in sanguinea the perception of the 
cases in which I am inclined to believe that Wasmann has ae overestima 
the power of association in ants. His statement, however, as he bim 
which I gave a fabulous number of Z. pratensis cocoons during the course 
summer failed to rear a single one. The same was true of several other formi- 
caries to which I gave fewer cocoons." 
HTC cy cay 
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