710 THE AMERICAN NATURALIST. [Vor. XXXV. 
S. testaceus is a commoner and better known form than 
S. huberi, and is supposed to represent a further advance 
towards a condition of social parasitism. The number of workers 
of S. testaceus is decidedly smaller in proportion to the number 
of Tetramoriums. On this account Forel maintains that the 
worker cast of S. ¢estaceus is on the road to disappearing 
(cf. Anergates !). As fighters these workers, though provided 
with sabre-like mandibles, are indeed but sorry caricatures of 
Polyergus and decidedly less valiant than the workers of 
S. huberi. They do not kill the Tetramoriums, but seem to 
frighten them into deserting their larvae and pupz. Their 
weakness is further shown by the fact that they do not under- 
take their pillaging expeditions alone, but accompanied by their 
Tetramorium auxiliaries, and it is these latter that determine 
the success of the enterprise undertaken for the sake of rob- 
bing their own species. The workers of S. Zeszaceus are even 
awkward in their attempts to carry away the conquered larva 
and pupe. Although the Tetramorium auxiliaries commonly 
do all the work within the nest, such as excavating the galleries, 
caring for the larvae and pupz, and feeding the Strongylog- 
nathus, the latter are, nevertheless, able to feed themselves 
and to dig the nest, but they are apparently unable to care 
for the young. 
Forel and Wasmann have succeeded in throwing consider- 
able light on the obscure problem of the origin of the S. tes- 
taceus-Tetramorium colonies. The former found a single 
fertile queen of the Strongylognathus living amicably in the 
midst of a colony of Leptothorax acervorum ; and Wasmann 
made the significant discovery of a fertile queen of the Stron- 
gylognathus and a fertile queen of Tetramorium living side by 
side in the same nest. This nest contained workers of both 
species (15,000-20,000 Tetramoriums and some thousands of 
Strongylognathus), and pupz, about 70% of which were males 
and females of Strongylognathus. The remainder included 
two large male pupz of Tetramorium. From this discovery 
Wasmann infers that the mixed nests of .S. testaceus-Tetra- 
morium are alliance colonies brought about by the adoption of 
fertilized queens of Strongylognathus by Tetramorium colonies. 
