50 
William Morton Wheeler 
recurved in the amber form. Moreover, the worker E. antiqua bears 
the same relation in size to Mayk’s type specimen and the male de- 
scribed above, as does the worker E. longi to its female and male. 
I believe, therefore, that I cannot be mistaken in my generic diagnosis. 
E. antiqua, as we must now call the species, acquires a peculiar 
interest from the fact that hitherto only two species of the genus 
have been described, one (E. longi) from Texas, and the other (E. peru- 
viana Emery), from Peru. Only the female of the latter has been 
seen. Since no species of the genus has been described from the Old 
World, it would be easy to jump to the conclusion that we have here 
a striking resemblance between amber and neotropical forms, but this, 
in my opinion, would be premature, f'or the recent Erebomyrmce seem 
to be very rare ants, and it is not at all improbable that living 
species may yet be discovered in the tropics of the Old World. The 
discovery of species in such widely separated localities as Texas, Peru 
and the Baltic region proves, nevertheless, that the genus was once 
cosmopolitan. 
E. antiqua is interesting also from an ethological standpoint. 
Its pale, diminitive workers, with their vestigial eyes, show very 
clearly that it was a hypogseic ant, the large, pigmented sexual forms 
of which appeared above the surface of the ground only for their 
nuptial flight. Emery, Forel and others have shown that several 
species of the allied genera Äeromyrma, Carebara and Diplomorium 
in the Old World, of Tranopelta in the New World, and of Solenopsis 
in both hemispheres live as thief-ants in the nests of other Formicidse 
and of termites. As the type specimens of E. longi were taken near 
termite nests by Mr. W. H. Long, and as termites are known from 
the amber, we may safely infer that in its habits E. antiqua closely 
resembled its living Texan congener. iSocial symbiosis and parasitism 
in ants, therefore, are not necessarily recent acquisitions but may date 
from the early Tertiary or even from. the Mesozoic. 
The very small size of the worker of E. antiqua as compared 
with the male and female would seem to indicate that - the species 
once possessed polymorphic workers like Pheidologeton , Oligomyrmex , 
Äeromyrma and a few species of Solenopsis , but had already lost all 
but the smallest caste of these sterile forms during Oligocene times. 
If this view of the origin of the discrepancy in size between the 
workers and queens, which is held by Emery, is correct, the hypothesis 
which I advanced in a former paper (1908) to the effect that the 
polymorphism of the worker caste is of more recent origin than the 
Oligocene, will have to be abandoned. 
