318 
Psyche 
[Vol. 95 
reared both morphs, the replacement queen only produced inter- 
morphic females. 
Of the 222 colonies of Leptothorax spec. B two contained a single 
queen and brood only, and a third one consisted of two fertile 
females and brood. Three more colonies might have been incipient, 
too, but here one worker had already eclosed. However, 7 of 14 
colonies of a dark brown ant morphologically similar to L. spec. B, 
which were collected near Vancouver, B.C., in August 1988, were 
found without workers. 
Discussion 
The ant tribe Leptothoracini consists of several hundred species 
of small- to medium-sized ants, which form colonies of several 
dozen to few hundreds of workers. It exhibits a rich variety of 
different social structures and colony foundation behaviors. Apart 
from social parasites, which may be inquilines, degenerate slave- 
makers, active dulotes, and xenobiotic guest ants, the non parasitic 
species have been found to be obligatorily monogynous, function- 
ally monogynous, or facultatively polygynous (Buschinger, 1974a). 
We here report on functional monogyny and polygyny in some 
species of the subgenus Leptothorax s.str. M. R. Smith (= Mycho- 
thorax Ruzsky) from North America. Between 20 and 30 percent of 
the colonies of L. retractus, L. spec. B, and L. spec. C are truly 
polygynous. The fertility of several inseminated females has been 
proven by dissection; in a number of cases, egg-laying has been 
directly observed. In Leptothorax spec. A, about one-fourth of all 
colonies with intermorphic queens contained additional, insemi- 
nated females, again mostly intermorphs, which in almost all cases 
have been found to be sterile. An occasional polygyny in Lepto- 
thorax spec. A cannot be ruled out but it seems to be very rare. 
There are two important differences between functional mono- 
gyny in polistine wasps and in Leptothoracini. In Polistes gallicus, 
Pardi (1940; 1946) had observed that when two females cooperate in 
colony foundation, the more aggressive one becomes queen, and the 
subordinate one becomes worker. In colonies with several females, 
however, ovary size and fertility correspond to the female’s rank in a 
dominance hierarchy. Several females may lay eggs, though in dif- 
fering degrees, and functional monogyny is sometimes guaranteed 
only by differential egg consumption by the dominant a-female 
