280 
Psyche 
[September-December 
the parasite queen are ordinary in size and behavior in compari- 
son with other Formica, and they gradually supplant the host 
workers until a pure, newly independent parasite colony comes 
into existence. In short, most of the species of the microgyria 
group appear to be temporary social parasites. 
Wing (1949) described F. dirksi from a single queen found in 
the nest of a Formica fusca (form “ subaenescens”) colony in nor- 
thern Maine. Because of the absence of microgyna-gr oup workers, 
he suggested that it might be a workerless social parasite. This 
may well be true, especially in view of the similarity now revealed 
between dirksi and talbotae. However, talbotae is the first well 
documented example of a workerless parasite in the genus. Both 
W. F. Buren and I have searched through extensive series of F. 
obscuripes containing queens and males of F. talbotae without 
finding a single microgyna-group worker, nor were such workers 
found in the North Dakota mixed series. In one thorough sur- 
vey of a mixed nest in Michigan, Talbot (1977) found only work- 
ers of F. obscuripes. It is reasonable to conclude, therefore, 
that either talbotae is entirely workerless or else its worker caste 
is so scarce as to restrict it to a state of permanent social para- 
sitism. 
Thus the significance of F. talbotae is that it completes the 
evolutionary sequence within Formica from complete indepen- 
dence through temporary social parasitism to permanent social 
parasitism, with an apparent total loss of the worker caste. It is 
worth noting also that so far as known other microgyna-group 
species, including dirksi, parasitize members of the fusca, neo- 
gagates, and pallidefulva groups of Formica, whereas talbotae 
is associated with a member of the rufa group. This difference 
may prove significant with reference to the extreme state of social 
parasitism achieved by talbotae, although the data are still too 
few to establish host specificity with any degree of confidence. 
Acknowledgments 
I wish to thank Mary Talbot, William F. Buren, and Paul B. 
Kannowski for supplying me with the specimens described here, 
Akey C. F. Hung for providing data on the Iowa series, and David 
R. Smith for the loan of the unique holotype of F. dirksi. The 
study has been supported by National Science Foundation Grant 
no. BNS73-00889. 
