1977] Buschinger & Alloway — Harpagoxenus americanus 241 
to test our hypothesis that all Harpagoxenus queens and workers 
produced in “branch colonies” are derived from larvae taken from 
“primary colonies.” 
Summary 
During the summer of 1977, we collected numerous colonies of 
the slave-making ant Harpagoxenus americanus in southern On- 
tario and northern Ohio. The numbers of dealate Harpagoxenus 
queens, intermorphs, and workers were recorded; and the produc- 
tion of young Harpagoxenus workers and sexuals were observed in 
41 colonies. Some of the Harpagoxenus queens, all the inter- 
morphs, and most of the Harpagoxenus workers were dissected to 
determine the structure and function of their reproductive organs. 
The queens, intermorphs, and most of the workers have 6 ovarioles. 
However, since only alate and dealate full queens have a spermath- 
eca, they are the only individuals that can be inseminated. Thus, 
no true ergatoid queens exist in H. americanus. Nevertheless, many 
workers have functional ovaries and lay eggs, sometimes even in 
queenright colonies. We found 3 incipient colonies, 13 queenright 
colonies, and 23 “branch colonies” that lacked a dealate queen but 
contained one or more fully or partially fertile workers. Younger 
“branch colonies” produce males, queens and workers, supposedly 
from larvae of their “mother colony,” older “branch colonies” only 
yield males. The significance of this population structure is dis- 
cussed. 
Literature Cited 
Alloway, T. M. 
[1978] Raiding behaviour of two species of slave-making ants, Harpagoxenus 
americanus (Emery) and Leptothorax duloticus Wesson (Hymenoptera: 
Formicidae). Animal Behaviour, in press. 
Buschinger, A. 
1973. The role of daily temperature rhythms in brood development of ants 
of the tribe Leptothoracini (Hymenoptera: Formicidae). In: Effects of 
Temperature on Ectothermic Organisms. Ed. W. Wieser, Springer 
Berlin-Heidelberg-New York, pp. 229-232. 
1975. Eine genetische Komponente im Polymorphismus der dulotischen 
Ameise Harpagoxenus sublaevis. Die Naturwissenschaften 62: 239. 
[1978] Genetisch bedingte Entstehung gefliigelter Weibchen bei der sklaven- 
haltenden Ameise Harpagoxenus sublaevis (Nyl.) (Hym., Form.). Ins. 
soc., in press. 
