1978] 
Burnham — Social Insects in Fossil Record 
103 
(Lower Oligocene). In addition, it must be remembered that the 
Paleocene did not begin for at least 40 million years after the 
appearance of Sphecomyrma freyi. 
Eocene 
Very few fossil ants have been found in deposits of this age, and 
the determinations of many of these ant species are in doubt. 
Scudder (1877, 1878) described four supposed ants from the Green 
River formation, and five ants (1877) from the Quesnel Beds in 
British Columbia. Generic identifications on all of these fossils are 
to be considered dubious at best, and more likely incorrect (Car- 
penter, 1930). 
In 1920, two species, Oecophylla bartoniana and Formica heter- 
optera, were described by Cockerell from an Eocene deposit in 
Bournemouth, England. Wheeler (1928) considered these ants for- 
micines, but because the descriptions were based on wing fragments, 
he questioned their generic determinations. Similarly, Cockerell’s 
Formica eoptera (1923a) from the Eocene of Texas is of uncertain 
position at both the generic and subfamily levels. Archimyrmex 
rostratus (Cockerell, 1923b) from the Eocene shales of Colorado is 
probably a myrmicine (Carpenter, 1930), and is the only Green 
River ant that can be placed with any certainty in a subfamily. 
Carpenter (1929) described Eoponera berryi from the Wilcox 
formation of Tennessee, and placed this ant in the subfamily 
Ponerinae. He suggests that it may be closely allied to the Neotrop- 
ical genus Dinoponera. This is of interest because Eoponera berryi 
is the oldest known ant (Lower Eocene) to be assigned to a living 
subfamily of Formicidae. 
Wilson (personal communication) mentions the recent discovery 
of three ants in a Middle Eocene amber deposit near Malvern, 
Arkansas, each belonging to a different subfamily. One belongs to 
the Dolichoderinae, genus Iridomyrmex; one is a formicine closely 
allied to the genus Paratrechina, and considered a relatively primi- 
tive, or “typical euformicine”; the last is a new genus of myrmicine, 
unique by virtue of its inflated postpetiole. These ants have yet to be 
formally described but they are nevertheless of paramount interest. 
The presence of these subfamilies in North America in the Eocene is 
strongly suggestive of their rapid evolution and dispersal during the 
Paleocene and perhaps during the Cretaceous. 
