1927] The Social Parasitism of Harpagoxenus americanus 7 
queens. These differ from the workers in the same ways as do 
the queens of most ant species. In addition, however, I have 
found a number of workers with rudimentary ocelli. Such 
specimens were present, for example, in nests 1 and 5. Usually 
the ocelli are represented in these specimens only by small 
chitinized humps, but sometimes small lenses are present. 
The number of these rudiments varies from one to three ; the 
majority of workers do not show any trace of ocelli. Since 11 
of the 17 nests found (and three of the four recorded by Emery 
and Wheeler) contained no dealated queens, one is led to suspect 
that H. americanus, like H. sublsevis, has fertile worker-like 
females. This view is borne out by observations made on nest 
number 4. The only adult Harpagoxenus in this nest was a 
worker that had two small rudimentary ocelli. When collected, 
only one egg was found in the nest, but two days later four eggs 
were present. This observation is not conclusive, since it is not 
possible to be certain that the three eggs in question were not 
present all the time; and even if they were newly laid the Lep- 
tothorax workers may perhaps have produced them. I have 
dissected three workers (Harpagoxenus) from nest number 9. 
There were three ovarioles present in each ovary in all three 
specimens, and a sac arising from the anterior end of the common 
oviduct in every specimen is evidently the seminal receptacle. 
No spermatozoa were present, and no eggs were differentiated in 
the ovaries; but these specimens came from a nest that had an 
old queen, and they had been kept alive in the laboratory for 
three months, so the ovaries may not have been in normal con- 
dition. The evidence thus indicates that H. americanus has 
fertile worker-like females. It remains to be discovered whether 
these females infect new colonies by the method Yiehmeyer 
supposes to occur in H. sublsevis. This author surmises that 
such ergatoid forms take part in raids, and then remain in the 
raided nest and appropriate the remnants after their nest-mates 
have returned to the home nest. 
It will be seen from table 1 that sexual forms of Leptothorax 
were present only in nest number 4, which contained two queen 
and one male pupse. The two former emerged after the nest 
was brought into the laboratory. They were cared for by the 
