POPULATION STRUCTURE AND POLYMORPHISM 
IN THE SLAVE-MAKING ANT 
HARPAGOXENUS AMERICANUS (EMERY) 
(HYMENOPTERA: FORMICIDAE) 
By Alfred Buschinger 1 and Thomas M. Alloway 2 
Fachbereich Biologie, Institut fur Zoologie, 
der Technischen Hochschule, D6100 Darmstadt, Schnittspahnstr. 3; 
and Erindale College, University of Toronto, 
Mississauga, Ontario, L5L 1C6, Canada 
Introduction 
The biology of the slave-making ant, Harpagoxenus americanus, 
has been studied by several previous investigators. Creighton (1927, 
1929) described slave raids and performed some experiments on 
colony foundation. Wesson (1939) provided a classic account of 
numerous aspects of the natural history of H. americanus including 
its distribution, colony demography, hibernation, brood develop- 
ment, and its colony-foundation, mating, and slave-raiding behav- 
iours. Alloway (in press) provides a detailed account of its raiding 
behaviour in comparison to that of the closely related, but more 
primitive, species Leptothorax duloticus. 
Wesson (1939) found that, in addition to a rather small propor- 
tion of “normal” queenright colonies, there are many queenless 
“branch colonies” which sometimes contained apparently fertile 
“gynecoid” workers. Moreover, he observed the formation of such 
“branch colonies” as a consequence of slave raids which occurred 
late in the raiding season. Previously, Sturtevant (1927) had dis- 
sected americanus workers and found that they typically have 6 
ovarioles and “a sac arising from the anterior end of the common 
oviduct” which he interpreted as being a seminal receptacle. Sturte- 
vant also found some workerlike individuals with rudimentary ocelli 
and presumed that H. americanus, like the European H. sublaevis, 
has ergatoid queens. However, Wesson (1939) wrote that he had 
Supported by a grant from the Deutsche Forschungsgemeinschaft. 
Supported by Grant A0301 from the National Research Council of Canada. 
Manuscript received by the editor April 27, 1978. 
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