1977] Buschinger & Alloway — Harpagoxenus americanus 239 
which Sturtevant interpreted as being the spermatheca in the H. 
americanus workers that he dissected was in fact the Dufour’s gland. 
Thus, in H. americanus as in H. canadensis (Buschinger & Alloway, 
in press), only the initially alate full queens possess a spermatheca 
and are capable of being inseminated. In this respect, both North 
American species differ radically from the European H. sublaevis 
in which true ergatoid queens are very common (Buschinger, 1975, 
1978, in press). 
H. americanus populations consist of both monogynous, queen- 
right “primary colonies” and queenless “branch colonies.” In most 
locations, the “branch colonies” outnumber the “primary colonies” 
by a ratio of approximately 2:1. In accordance with the observa- 
tions of Wesson (1939), we assume that the “primary colonies” are 
founded by single, newly fecundated H. americanus queens which 
penetrate small host-species colonies, usurp the place of the host 
queens, and begin to lay eggs. A first brood of americanus workers 
is then reared with the assistance of host workers. Subsequently, 
the supply of host workers is augmented by slave raids in which 
both the americanus workers and their slaves participate (Wesson, 
1939; Alloway, in press). Late in the summer, some of these raids 
terminate in the formation of “branch colonies” by some of the 
americanus workers and their slaves (Wesson, 1939). However, 
despite Wesson’s failure to observe the phenomenon in the labora- 
tory, we suggest that, in the process of forming “branch colonies,” 
the americanus workers and their slaves carry across a certain num- 
ber of americanus larvae from the “primary colony” to their new 
nest. Most of these larvae mature to become workers, alate queens, 
and males the next summer. At the same time, one or more of the 
“branch colony” workers become fertile and begin laying eggs 
which develop into males during subsequent years. However, a few 
of the female larvae from the “primary colony” may undergo an 
additional hibernation before maturing to become queens or work- 
ers, a process which would explain Wesson’s (1939) observation 
that “branch colonies” occasionally produce small numbers of 
queens and workers even in the second year in the laboratory. 
Such double hibernations are known to occur in Harpagoxenus 
sublaevis and its host species (Buschinger, 1973). Although we 
cannot definitely rule out the parthenogenic production of females 
in H. americanus , our supposition that the phenomenon does not 
occur affords (in addition to the advantage of simplicity) an ex- 
