Tabanus eggeri was created in 1868.
Tabanus glaucopis was created in 1820.
Tabanus cordiger was created in 1820.
Tabanus lineola was created in 1794.
Tabanus miki was created in 1880.
Tabanus bovinus was created in 1758.
Tabanus sudeticus was created in 1842.
Tabanus nigrovittatus was created in 1847.
Tabanus darimonti was created in 1964.
Tabanus autumnalis was created in 1761.
The scientific or taxonomic name would be Tabanus spp.
It depends on the species of horsefly. Some species are quite small under 1/2". The largest horsefly in North America is the Tabanus atratus or Giant Horsefly. They are often over 1.5" and it isn't uncommon to find them over 2". http://images.whatsthatbug.com/images/black_horsefly_ruler.jpg Has a picture of a Giant Horsefly that is slightly over 2".
The scientific name for horse fly is Hybomitra micans. The horse fly belongs to the diptera order and the brachycera suborder.