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Bulletin American Museum of Natural History. [Vol. XXII, 



3. The females of some of the species of the sanguinea group, 

 such as F. pergandei and the different subspecies and varieties of F. 

 sanguinea, are dulotic and appear to secure the workers needed for 

 bringing up their first brood by robbing the young of ants belonging to 

 the jusca or pallide-fulva groups. 



Thus the colonies of the ubiquitous, very cowardly, highly adaptable 

 and extremely fertile F. fusca and F. schaufussi furnish a wide-spread 

 substratum, so to speak, on which at least many of the species of 

 Formica belonging to the rnja, exsecta and sanguinea groups have 

 molded their parasitic habits. These species have learned to exploit 

 the jusca and schaufussi in manifold ways — to use them either merely 

 as nurses for their firstling progeny (temporary social parasitism), 

 or as a permanent food supply and source of auxiliary workers (du- 

 losis). The parasitism thus inaugurated in the genus Formica has 

 been developed to its extreme in the allied highly dulotic genus Poly- 

 ergus, the members of which are abjectly dependent on fusca or 

 schaufussi workers for their food, for the care of their young, and even 

 for the excavation of their nests. 



Fig. I. Artificial ant nest, constructed on the combined principles ot the _Fielde_ and Janet 

 nests; with one of the roof-panes removed, r, plaster of Paris base, cast in a single piece; 

 c, entrance to be plugged with cotton after the admission of the ants from the Forel arena; 

 m, glass roof-pane, resting on Turkish towelling (5); a, opening between the two chambers; 

 n, manger; a cup-shaped depression in the plaster base; e, slice of sponge, which is kept wet. 

 The plaster base measures 20 X 25 cm. 



Inasmuch as the parasitic instincts of these various ants are trace- 

 able to the very first foundation of the colony, and since this, as has 

 been abundantly shown in the preceding paragraphs, is the work of the 

 female ant, I have concentrated my experiments on the instincts of this 

 sex, although some miscellaneous notes on nesting habits and other 

 ethological matters which fell under my observation at the same time, 

 have been included in the following pages. 



For purposes of study I have used an artificial nest combining the 

 Fielde and Janet patterns (Fig. i) . Of the former I have retained the 



