Horse And Deer Flies

The earliest classifications of the Tabanidae divided the family into two subfamilies based on the presence or absence of hind tibial spurs (Loew 1860; Lutz 1905, 1909, 1913; Surcouf 1921). This organisation underwent several changes based on single characters (Enderlein 1922, 1925b). By ~1950, most workers had reverted back to Loew’s concept and settled on two subfamilies, the Pangoniinae (with tribes Pangoniini, Scepsidini, Chrysopini. Note: early workers, including Mackerras, used the spelling stem ‘Chrysop-’, which is an objective junior homonym to a group of neuropterans (ICZN 1968). The stem ‘Chrysops-’ is now used) and the Tabaninae (with tribes Haematopotini, Tabanini, Diachlorini and variously five others) (Bequaert 1930; Fairchild 1942; Philip 1947, 1950; see Fig. 2a).

Unfortunately, the presence of the hind tibial spurs is variable within the Pangoniinae, adding uncertainty to an already taxonomically challenging group. Mackerras (1954) attempted to single-handedly solve this issue by exploring genital characters in Tabanidae. His work came shortly after Hennig (1950) published his first version of Phylogenetic Systematics in German and before Hennig’s concepts of cladistics began to take hold among the scientific community following the English translation (Hennig 1966). Mackerras (1954: p. 431) felt that division by the presence of hind tibial spurs placed the ‘chrysopines unhappily with the pangoniines, and separated them from the tabanines, to which they seemed to me to be much more closely related’. Examination of genitalia convinced him that the Chrysopsini was indeed more closely related to the Tabanini than to the presumably more ancient and plesiomorphic Pangoniini. As such, he proposed the first phylogenetic hypothesis for the Tabanidae based on what he believed to be shared, derived characters (synapomorphies). In this scheme, the Tabanidae contained the Pangoniinae, Scepsidinae, Chrysopsinae and Tabaninae, with the latter two as sister taxa (see Fig. 2b). In the words of Philip (1957: p. 550) this began ‘a new era’ in Tabanidae systematics. Mackerras also suggested that the Chrysopsinae was intermediate, with the Tabaninae evolving from it as a more recent group. This can only be shown if reciprocal monophyly by extinction has failed to occur leaving the Chrysopsinae paraphyletic.

Currently, most authors accept a classification based on Mackerras’ hypothesis and adopt the following subfamilies and tribes: Chrysopsinae (Bouvieromyiini, Chrysopsini, Rhinomyzini), Tabaninae (Diachlorini, Haematopotini, Tabanini), and Pangoniinae (Pangoniini, Philolichini, Scionini) (Chainey 1993). Scepsidinae is a controversial subfamily of four monotypic genera that share a lack of functional mouthparts in adults (Oldroyd 1957; Fairchild 1969; McAlpine 1981; Fairchild and Burger 1994). They only occur in the coastal sands of south-east Africa and Brazil and are considered by most authors to be grouped based on convergent morphology. Some authors also support the Mycertomyiini as a fourth tribe under Pangoniinae based on its bizarre genital structure (Coscarón and Philip 1979; Fairchild and Burger 1994).

There are about 4,500 species of horse fly. These flies are known for the painful bite that many have. Horse flies mostly eat nectar, but females must eat blood before laying eggs. The black horse fly lives mostly in the eastern US. It often attacks farm animals, causing serious blood loss. It can also carry diseases that harm animals and people.

These species do not currently belong to a generic classification, and are considered incertae sedis, Latin for "of uncertain placement.