1932 ] 
Distribution of Formica ulkei 
127 
LOCAL DISTRIBUTION OF FORMICA ULKEI MOUND- 
NESTS WITH REFERENCE TO CERTAIN 
ECOLOGICAL FACTORS 1 
By W. A. Dreyer 
Department of Zoology, University of Cincinnati 
and 
Thomas Park 
Department of Zoology, University of Chicago 
Introduction 
The existence of a number of mound-nest colonies of the 
ant Formica ulkei Emery at Palos Park, Illinois, has been 
known for several decades. In recent years various phases 
of ecology and physiology of this ant and its nests have 
been analyzed and published. Holmquist (1928) reported 
at length on its life-history and hibernation ; Orlando Park 
(1929) discussed certain myrmecocoles associated with it 
in the nests ; Thomas Park (1929) reported the occurrence 
and behavior of a thief -ant intimately found in the mounds, 
and Dreyer (1932) has analyzed certain aspects of the res- 
piratory behavior of this ant in relation to its hibernation. 
Up to the present time no accurate description of the ex- 
tent and distribution of these mounds has been attempted. 
In this paper they will be discussed with reference to their 
individual form, their distribution, and certain environ- 
mental factors correlated with this distribution. 
1 The authors take pleasure in acknowledging; their appreciation to 
Professor W. C. Allee, of the University of Chicago, for his kindly 
aid and criticism of this work. 
