1964] 
Wilson and Taylor — Fossil Ant Colony 
97 
special aspects of the ecology and physiology of O. smaragdina. Vari- 
ation and taxonomic relationships of the two species are discussed in 
the reviews of Emery (1921) and Wheeler (1922). 
Oecophylla is well represented in Tertiary fossil deposits. O. brish- 
kei Mayr, which closely resembles the modern forms, is moderately 
abundant in the Baltic amber, of Eocene age. It was represented by 
50, or 0.4% of all of the 11,678 Baltic amber ants examined by G. 
Mayr and W. M. Wheeler jointly (Wheeler, 1914). A second, more 
divergent species, O. brevinodis Wheeler, was represented in the col- 
lections by a single specimen. Another species, O. sicula Emery, has 
been described from Upper Miocene deposits in Sicily. The species 
thus far mentioned form a morphocline in the increase of length of 
the legs, antennae and petiole, and the narrowing of the metathoracic 
constriction. This morphocline, which follows the geologic sequence, 
runs as follows: brevinodis — > brischkei — » sicula —> longinoda 
(together with smaragdina) . It seems reasonable to conclude that 
the species exhibit the approximate phylogenetic succession that must 
have occurred in the evolution of the modern species of the genus. 
O. leakeyi is a somewhat divergent member with reference to this 
succession, in its larger size and retention of ocelli in the major 
worker caste. It would appear to fall nearest to brischkei in the 
degree of mesosomal and appendage elongation. Two other species 
have been named on the basis of queens found in the Miocene 
shales of Europe: O. obesa radobojana (Heer) from Radoboj, 
Croatia; and O. praechara (Foerster) from Brunstatt, Alsatia. The 
precise relationships of these forms cannot be determined, although 
Mayr (cited by Wheeler, 1914) stated that radobojana cannot be 
distinguished from smaragdina. No New World fossils of Oeco- 
phylla are known, and the genus is notably absent from the rich 
Miocene collections from Florissant, Colorado, described by Car- 
penter (1930). 
In sum, the picture that emerges of Oecophylla is that of a morphol- 
ogically stable Old World genus that has persisted through most of 
the Tertiary with very little speciation. Oecophylla is related to at 
least two other relict, arboricolous Old World genera that date to the 
Eocene: Dimorphomyrmex and Gesomyrmex. Furthermore, it is not 
far distant from Gigantiops, a remarkable terricolous genus now limit- 
ed to the South American rain forests. It seems appropriate to regard 
Oecophylla as both specialized and caught in an evolutionary cul-de-sac. 
We can speculate that its unique specializations have permitted it to 
remain abundant and widespread — but at the expense of blocking 
further significant evolution and speciation. 
