1977] Buschinger & Alloway — Harpagoxenus americanus 235 
Table I. Occurrence of Lepothorax longispinosus and L. ambiguus as host species 
in colonies of H. americanus. 
H. americanus with slave species 
colonies L. longispinosus L. ambiguus L. Long. + L. amb. 
incipient 2 
queenright 12 
queenless 13 
of factors such as the type of vegetation, surface drainage, the dis- 
tribution of habitable nesting sites, etc. Sturtevant (1927) recorded 
an infestation rate of 13% for H. americanus (i.e. 17 americanus 
colonies to 132 colonies of one of its three host species, Leptothorax 
curvispinosus Mayr). In the areas where we collected our material, 
the host species were Leptothorax ambiguus Emery and L. longi- 
spinosus Roger. Although ambiguus was generally the more abun- 
dant of the two host species in acorn and hickory-nut nests, longi- 
spinosus was more frequently enslaved (Table I). These data sug- 
gest that colony-founding Harpagoxenus queens preferentially seek 
out longispinosus colonies but that established Harpagoxenus col- 
onies, especially the so-called “branch colonies,” raid the nests of 
both hosts. 
Our material consisted of a total of 41 Harpagoxenus colonies 
or “branch colonies” in the sense of Wesson (1939). Thirteen “pri- 
mary colonies” contained a dealate full Harpagoxenus queen and 
from 1 to 8 Harpagoxenus workers. The average number of Har- 
pagoxenus workers in these colonies was 3.0. Three incipient col- 
onies contained only a Harpagoxenus queen, several host-speices 
workers, and a brood which consisted of Harpagoxenus worker 
pupae or larvae which developed into Harpagoxenus worker pupae. 
The 25 “branch colonies” lacked a dealate full queen but contained 
from 1 to 9 Harpagoxenus workers (with an average of 2.8), a 
variable number of host-species workers, and a brood. Six of these 
’’branch colonies” produced only male pupae of the parasite species; 
but the rest yielded female, worker, and male pupae of the parasite 
species. In one acorn which contained no adult Harpagoxenus 
when it was collected, there were nevertheless Harpagoxenus male, 
female, and worker pupae which were being attended by several 
longispinosus workers. Apparently, the Harpagoxenus adults had 
