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Psyche 
[March 
with certainty that these early vespids were social. Within the 
Vespidae, divisions into subfamily and tribe are based primarily on 
behavioral rather than morphological characters. Furthermore, the 
morphological differences between the castes in any given species 
are often not obvious in the preserved fossils. 
Oligocene 
True vespids are first found in the Upper Oligocene shales of 
Florissapt, Colorado and Rott, Germany, two highly productive 
fossiliferous deposits. These beds and other various localities listed 
in Table 3 have turned up an assemblage comprised of four genera 
and 14 species. It is quite remarkable that three of the four genera 
represented are extant and this supports the possibility that the 
Vespidae were essentially modern by the Oligocene. Furthermore, 
the diversification of taxa suggests a much earlier origin for the 
family than is evidenced by the fossil record. 
Miocene 
Scarcely any Vespidae are known from the Miocene, although 
this is most likely due to the overall dearth of deposits from this 
epoch. One vespid has been described from a deposit in Germany. 
This is Polistes kirbyanus and clearly belongs to the subfamily 
Polistinae. Other wasps from Miocene deposits have yet to be 
discovered, but one can assume that the wasp fauna of this age 
would be barely distinguishable from the wasp fauna of today. 
Formicoidea 
The following review of the fossil history of the Formicidae 
provides important information on their dominance, distribution, 
and supposed habits during the Mesozoic and Cenozoic eras. In 
contrast to the Vespoidea, ants are the most abundant insects in 
Tertiary formations. This may be attributed to their foraging 
behavior on and around trees, which enhances their chances of 
preservation in amber. A rough total of 20,000 specimens represent- 
ing some 200 species of ants has been studied (Table 4); this massive 
amount of work far exceeds the paleontological investigations 
carried out on any other family of insects. Several comprehensive 
monographs on the subject have been written, including The Ants of 
the Baltic Amber (Wheeler, 1914), and The Fossil Ants of North 
America (Carpenter, 1930), which are drawn on extensively in the 
following pages. 
