The unusual appearance of this fly tells us a lot about its life history. The flattened body (yes, it’s supposed to be that way, it hasn’t been squashed) allows the fly to slip between the feathers on its host, while keeping a low profile. Anyone that has been hiking locally may have dealt with ticks on their own body or that of a companion animal — ticks use that same flattened body shape to make themselves harder to remove. A flattened body shape (scientists refer to this as being dorso-ventrally flattened) helps prevent a parasite, in this case a fly, from being dislodged while it utilizes its food source — host blood. Feeding on the blood of another animal can be tricky business. Our BioSCAN scientists speculated that this fact (coupled with fly “old age”) may have contributed to this specimen’s tattered wings; perhaps the host tried to dislodge the feeding parasite and damaged it.
One look at the view from below and it becomes clear that the sclerotized proboscis (fancy entomology words for “tough mouthpart”) is undoubtedly painful; we don’t blame the bird for trying to get rid of it! Unfortunately for the pigeons, getting rid of these flies is not as easy as simply brushing them off. If you notice, the flies have long, curved claws on their feet. The last segments of insect legs are called the tarsi, and those claws are called tarsal claws. On most insects, these claws are small innocuous hooks — used for clinging to normal substrates. In these parasitic hippoboscids, however, these claws are enlarged with a pronounced curve to allow the fly to cling to its host — ouch!
So where did these flies come from? Originally, this species was found in the Old World tropics and subtropics, but today they have spread virtually worldwide on domestic pigeons and doves. Despite this wide range, we rarely see them — they spend most of their time flying around attached to their avian hosts. So rest assured, for as ominous as this bloodsucking fly may seem, they are solely interested in bird blood, not yours.