104 
Psyche 
[March 
O/igocene 
The Baltic Amber is, most certainly, the best studied of all 
Tertiary insect deposits, and has revealed a great deal about the 
nature and diversity of Oligocene ants. 6 As of 1928, 1 1,71 1 ants (93 
species) were examined from this deposit. Of this number, 1461 were 
studied by Mayr (1868); 690 by Andre (1895); and 9,560 by Wheeler 
(1914, 1928). 
An examination of the ant fauna reveals wide representation at 
the subfamily and generic levels. All extant subfamilies of Formici- 
dae are found in the amber with the exception of the Dorylinae and 
Leptanillinae. The absence of the Dorylinae is probably not due to 
selective exclusion on the part of the amber, but more likely 
indicates their absence from that part of the European continent 
during the Oligocene. Wheeler (1914) speculates that the foraging 
behavior of doryline ants should readily lead to entrapment in tree 
resin, but, in all probability, this group was then, as it is now, 
confined to the tropics. It is not surprising that the Leptanillinae are 
absent from the Baltic Amber; this is a small subfamily once 
considered a tribe of the Dorylinae, consisting of one genus and a 
few species; and although pantropical is hypogaeic and rarely 
encountered. 
The Dolichoderinae and Formicinae together constitute 97 per- 
cent of all specimens and evidence indicates that these amber ants 
were already extraordinarily specialized. Workers of Iridomyrmex 
goepperti were found in a piece of amber (originally in the Konigs- 
berg collection) with several aphids. On the basis of this discovery, 
Wheeler (1914) concludes that Homoptera were attended by ants 
then much as they are today. The finding of several genera of 
paussid beetles (e.g., Arthropterus, Cerapterites and Eopaussus) in 
the Baltic Amber (Wasmann, 1929) suggests that myrmecophiles 
were established at this time. Perhaps most remarkable of all was 
the discovery of two Lasius schiefferdeckeri workers — each found 
with a mite attached to the base of the hind tibia, in precisely the 
6 Because the Baltic Amber was secondarily deposited in a clay bed of Lower 
Oligocene age, it is necessarily older than the glauconitic sand (“blue-earth” clay) in 
which it lies. How much older is uncertain. In some published accounts it is referred 
to as Eocene. However, since the composition of the Baltic Amber ant fauna is very 
similar to that of the Florissant Shales and other bona fide Oligocene deposits, I am 
following Zeuner (1939, p. 26) in referring to the amber as Lower Oligocene. 
