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[Vol. 95 
in army ants. The evolution of the colony fission mode of reproduc- 
tion, a phenomenon common in army ants (e.g., Franks and Holl- 
dobler, 1987), was analyzed by Macevicz (1979) both from the kin 
selectionist and parental manipulationist point of view. Thus, in 
some cases workers might not suffer a loss in their own inclusive 
fitness by accompanying their sisters and rearing nieces and 
nephews instead of brothers and sisters. Workers, e.g., might select 
the queen with the higher life expectancy, instead of staying with 
their mother. In honeybees, the old queen leaves the nest and incurs 
the risks involved with founding a new colony, but almost no details 
are known about the circumstances of budding in Leptothorax ants. 
Allozyme data (unpubl. results) did not shown any evidence for 
inbreeding in Leptothorax spec. A, which would increase the 
relatedness between workers and their nieces. 
Additional field studies are under way to screen annual changes in 
colony and population structure of Leptothorax spec. A and to find 
out more about the success of colony foundation behaviors in dif- 
ferent habitats. 
Summary 
Data are given on the colony structure of some North American 
ant species belonging to the myrmicine subgenus Leptothorax s. str. 
The species studied by now are either functionally monogynous (i.e., 
sterile, inseminated females may accompany the queen, Leptothorax 
spec. A) or facultatively polygynous (i.e., several fully fertile, 
inseminated queens may contribute to the offspring). Incipient 
colonies of these species are rare in the field; young females 
probably return into conspecific colonies after mating in summer 
and found their own colonies by budding in spring. The behavior of 
young intermorphic and gynomorphic females after mating was 
studied in the functionally monogynous Leptothorax spec. A. In 
this species, queen replacement and colony fission were observed, 
too. 
Acknowledgments 
Parts of these studies were made possible by a grant from the 
NATO science council thru DAAD to J. H. We thank S. Cover, 
