84 
Psyche 
[June 
were present. Perhaps, therefore, C. kennedyi and creigh - 
toni represent a hitherto unknown type of social parasit- 
ism, in which the males and females of the parasite are per- 
mitted to develop to maturity in a host colony which not 
only retains its mother queen but also succeeds in rearing 
females and males of its own species. That the two para- 
sitic species of Crematogaster have been brought to light 
only very recently is not surprising, because all the worker- 
less parasitic ants are extremely rare. One of these, Epoe- 
cus pergandei Emery, described in 1894, from specimens 
taken by Pergande near Washington, D. C., is still known 
only from the types, notwithstanding long and diligent 
search for additional specimens by Dr. W. M. Mann, Dr. 
Creighton and myself. Moreover, the presence of worker- 
less parasites in a colony is very apt to be overlooked un- 
less the nest happens to be examined during the few days 
that intervene between the emergence of the parasites and 
their nuptial or dissemination flight. Since there is every 
reason to believe that both kennedyi and creightoni are 
derived phylogenetically from their respective host species, 
either by mutation or, more probably, by a gradual reduc- 
tion in size and fecundity of certain females (compare, for 
example, the series of temporary social parasites of the 
genus Formica, beginning with such forms as F. rufa and 
truncorum and ending in the North American species of 
the microgyna group), the parasitism of the two species of 
Crematogaster may be in a primitive phylogenetic stage, 
that is one in which the reduction in size and fecundity of 
the female is already accomplished but in which the host 
species has not yet acquired the habit of substituting the 
parasitic queen for that of its own species, as in certain 
other workerless species (Anergates, Bruchomyrma, etc.). 
Crematogaster ( Acrocoelia ) pilosa, the host of C. 
creightoni is not as well known as many of the other mem- 
bers of the lineolata “Formenkreis,” which has a wide dis- 
tribution, embracing Nova Scotia, Southern Ontario and 
the whole United States. Emery (1849) described only the 
worker pilosa as a subspecies of lineolata from specimens 
furnished by Pergande, who discovered it in the District of 
Columbia. It has since been recorded from Southern New 
Jersey and Florida. The specimens collected by Dr. 
