1946] 
Fossil Diptera from Florissant 
43 
SOME FOSSIL DIPTERA FROM FLORISSANT, 
COLORADO 
By A. L. Melander 
Riverside, California 
Florissant, near Pike’s Peak, Colorado, is a minor hamlet as 
towns go, but it is internationally renowned because of the 
multitude of Tertiary fossils that have been discovered near by. 
The small bluffs of laminated shale are being dug open piece- 
meal, to disclose layer upon layer of reminders of the living 
things of that region as they existed some twenty million years 
ago. The shale strata consist of solidified fine volcanic ash, 
blown out from adjacent volcanoes in Miocene times, with out- 
bursts of poisonous gases to overwhelm the insects and other 
life of that time. Many of the fossils are perfectly preserved, 
but the majority of the soft-bodied Diptera are tantalizingly 
incomplete. Here or there a specimen is discovered with 
enough of its taxonomic parts in good condition, so that it can 
be classified as accurately as a pinned recent fly. It is my privi- 
lege to announce some remarkable finds in this article. 
Silvius merychippi (Cockerell) (Tabanidae) 
Allotype, male. I purchased at the Museum at the Florissant 
fossil beds a beautiful specimen of what is unquestionably the 
species described by Professor Cockerell as Tabanus mery- 
chippi. The neuration of both wings is perfect and shows the 
maculations and course of the veins as originally described for 
the female. The abdomen, however, is not marked with the 
obscure median stripe, but is evidently uniformly testaceous. 
The shape of the first and fourth posterior cells indicate the 
genus Silvius rather than Tabanus. The broad yellow body and 
large size suggests the modern Silvius gigantulus , though the 
wings are like those of S. pollinosus. There is no angulation nor 
spur on the branch of the third vein, the wing, even with the 
markings, being like Figure 16, page 152, of Curran’s Manual 
of North American Diptera. 
