Belongs within: Tabanidae.
The Scionini are a group of horse flies characterised by the presence of apical spurs on the hind tibia, an undivided tergite 9, and male terminalia with a simple gonostylus (Pechuman & Teskey 1981).
Sciones of a blood-sucking line
Published 6 July 2026
Anybody who has been subject to the gentle attentions of a horse fly will probably not look upon them fondly. Even compared to other blood-sucking flies, horse flies are big, their bites are painful, and they are maddeningly persistent. But that does not mean that horse flies are without their points of interest, and among their notable subgroups are the austral tribe Scionini.
The Scionini include close to 300 species of horse fly found in Australasia and South America; a single North American genus Goniops has recently been excluded from the tribe (Lessard 2014). Fly taxonomy has a tendency to focus on genitalic features even over and above that applied to other insect orders, but horse fly taxonomy has long been a challenge because members of this family have far less elaborate genital structures than members of other families. Mackerras (1954) characterised the Scionini as having simple, finger-like styles on the hypopygium in males, and fairly undistinguished eighth sternites in females. Other characteristic features of the tribe typically include hairy eyes, and reduction or loss of an appendix to wing vein R4. Proboscises vary between species, some having a short proboscis that is shorter than the head, others having long proboscises that may reach twice the head length. Coloration is also variable: notable standouts include the often metallic species of the Australian genus Myioscaptia, or the boldly patterned, bumblebee-like South American Osca species.
Horse flies are most often thought of as blood-suckers but, as with other haematophagous flies, blood-sucking is a purely female pursuit. Males have weaker mouthparts than females and keep to a diet of flower nectar. Females may also take nectar; where flower associations have been recorded for Scionini, they seem to be associated with Myrtaceae and may function as pollinators. Some Scionini may never take blood at all; the South American genus Pseudomelpia has been described as entirely nectar-feeding. However, the Australian species Scaptia auriflua, which one can find described as a pure nectar-feeder in some places on the internet (and which is awarded the vernacular name of ‘flower-feeding March fly’), has been recorded as feeding from both flowers and humans (Lessard 2014). Larvae of horse flies are predators, attacking other small invertebrates. Where larvae of Scionini have been identified, they are found in damp soil, and may take multiple years to mature to adulthood.
Systematics of Scionini
<==ScioniniPT81 |--Goniops Aldrich 1892PT81, R00 | |--*G. hippoboscoides Aldrich 1892R00 | `--G. chrysocomaPT81 |--Mycteromyia Philippi 1865M54, R00 | |--*M. conica (Bigot 1857) [=Pangonia conica]R00 | |--M. albipectus Bigot 1892R00 | |--M. brevirostris Philippi 1865R00 | |--M. cinerascens Bigot 1892R00 | |--M. elegans Bigot 1892R00 | |--M. ensata Bigot 1892R00 | |--M. erythronotata Bigot 1892R00 | |--M. fusca Philippi 1965R00 | |--M. murina Philippi 1965R00 | |--M. nigrifacies Bigot 1892R00 | |--M. nitens Bigot 1892R00 | `--M. penicillata Bigot 1892R00 |--MelpiaM54 |--Pityocera Gigl.-Tos 1896M54, R00 | `--*P. festae Gigl.-Tos 1896R00 |--ListrioscaM54 |--ParoscaM54 |--ListraphaM54 |--OscaM54 |--PalimmecomyiaM54 |--PseudoscioneM54 |--Scione Walker 1850 [incl. Diclisa Schiner 1866]R00 | |--*S. incompleta (Macq. 1846) [=Pangonia incompleta, *D. incompleta]R00 | |--S. albifasciata (Macq. 1846) [=Pangonia albifasciata, Diclisa albifasciata]R00 | |--S. alluaudi Giglio-Tos 1895R00 | |--S. costaricanaB09 | |--S. distincta (Schiner 1866) [=Diclisa distincta]R00 | |--S. maculipennis (Schiner 1866) [=Diclisa maculipennis]R00 | |--S. misera (Osten Sacken 1886) [=Diclisa misera]R00 | `--S. singularis (Macq. 1846) [=Pangonia singularis, Diclisa singularis]R00 |--FidenaM54 | |--F. flavipennisB09 | |--F. nigrovittaB09 | `--F. sorbensM54 `--ScaptiaM54 |--S. adrelM54 |--S. aurataM54 |--S. aurifluaZS10 |--S. barbataM54 |--S. maculiventrisM54 |--S. patulaM54 `--S. viridiventrisM54
*Type species of generic name indicated
References
[B09] Burger, J. F. 2009. Tabanidae (horse flies, deer flies, tabanos). In: Brown, B. V., A. Borkent, J. M. Cumming, D. M. Wood, N. E. Woodley & M. A. Zumbado (eds) Manual of Central American Diptera vol. 1 pp. 495–507. NRC Research Press: Ottawa.
Lessard, B. D. 2014. Revision of the austral horse fly tribe Scionini (Diptera: Tabanidae). Austral Entomology 53: 203–239.
[M54] Mackerras, I. M. 1954. The classification and distribution of Tabanidae (Diptera). I. General review. Australian Journal of Zoology 2 (3): 431–454.
[PT81] Pechuman, L. L., & H. J. Teskey. 1981. Tabanidae. In: McAlpine, J. F., B. V. Peterson, G. E. Shewell, H. J. Teskey, J. R. Vockeroth & D. S. Wood (eds) Manual of Nearctic Diptera vol. 1 pp. 463–478. Research Branch, Agriculture Canada.
[R00] Ricardo, G. 1900. Notes on the Pangoninae of the family Tabanidae in the British Museum collection. Annals and Magazine of Natural History, series 7, 5: 97–121, pl. 1.
[ZS10] Zborowski, P., & R. Storey. 2010. A Field Guide to Insects in Australia 3rd ed. Reed New Holland: Sydney.