Tabanus abdominalis

Specimens of T. abdominalis have proved difficult to identify due mainly to the variation between individuals and the similarity to other variable species, particularly T. limbatinevris and T. sulcifrons but including T. gladiator and T. nefarius . Osten Sacken (1876) was aware of the difficulty of delimiting the variation of T. abdominalis . He described the species from 3 females which I take to be nearest to the original type of Fabricius's description. He then described different forms from 14 females which may be either mere varieties or distinct species. However, in 1878, Osten Sacken re-described T. abdominalis from 19 females from Kentucky and Georgia, stating that As my description of T. abdominalis was principally based on a small and very abnormally colored specimen, I prefer to give a description of both species. The 2nd species he refers to was thought by him to be Tabanus sulcifrons . Pechuman et al (1983) believe Osten Sacken's earlier (1876) description was actually based on a specimen of T. limbatinevris and not T. sulcifrons . Jumping ahead to 1990, Hoppe et al. (1990) proved the distinctiveness of T. abdominalis, T. limbatinervis , and T. sulcifrons based on an analysis of cuticular hydrocarbons (Internet ref below). At the present time it is probably impossible to separate these 3 species based solely on photographs. Museum specimens stand a good chance of being identified based on measurements of the ratio of length of the frons divided by its length, the condition of the 5th posterior cell in the wing, and the length:width ratio of the palps (Pechuman et al. 1983).