March flies have large heads and huge eyes with up to tens of thousands of individual facets. ( zoom in on eyes in this photo for details) However they don’t use eyesight to find their victims. Instead they are attracted to the carbon dioxide humans exhale. As the fly gets closer to the target it is drawn by other clues like body heat , odours and dark colours. Like mosquitoes only the females bite because they need protein from our blood for egg development.
March fly bites really hurt because march flies use large wide rasping proboscis suitable for biting hides thicker than ours. An allergic reaction to their saliva causes the itch. No known human diseases are carried by the Australian March flies but they can be very annoying .