Australian Common March Fly - Tabanus australicus
Females of most horse flies require a blood meal to develop their eggs. Most feed on mammals but some species feed on birds, amphibians or reptiles. Some are pests of humans and stock. If the flies are very abundant, blood loss can be a problem for stock. In Australia, horse flies are only known to transmit a nematode to kangaroos and wallabies. One Australian species are known to cause sensitisation, with a severe reaction to subsequent bites in humans.
Adult horse flies feed on nectar and sometimes pollen, and can be good pollinators. In some Australian species, the females only feed at flowers and do not suck blood. Horse fly larvae are predators of other invertebrates usually in the soil in wet areas.
(Text Source: Wikipedia)