The secret life of the rhino bot fly
During a recent trip to the bush, I witnessed a peculiar incident: a large wasp scurrying about on the face of a white rhino. It looked like a spider-hunting wasp. At first I presumed that this incident was coincidental. I thought the rhino must have brushed against some vegetation and picked up the opportunistic invertebrate hitch-hiker. But a few weeks later, I noticed the same thing on two other rhinos… I contacted entomologist Duncan MacFadyen – well known to go! readers – who put me in contact with professor Mike Picker from the University of Cape Town. Mike told me something interesting: The “wasps” were in fact rhino bot flies from the family Gasterophilidae (meaning stomach-loving) and they’re Africa’s largest flies. The larvae live in the gut of a rhino, where they feed on the mucosal membrane. They’re passed out in the rhino’s droppings and pupate to emerge as adult flies. The flies themselves don’t feed – they just reproduce – and they live very short lives as a result. Because of this they are seldom seen. Other flies in the same family lay their eggs in the facial fur of their hosts and the unsuspecting animals ingest the eggs while grooming. It was thought that the rhino bot fly reproduced in the same fashion but there was no evidence to support this assumption. That is, until I sent Mike these photos! You can clearly see an adult fly laying eggs on the rhino’s face in some of my photos. The flies are harmless and do indeed mimic spider-hunting wasps, possibly to confuse predators and extend their already short adult lives. This incident proves that there’s always something new to discover in nature. Rhinos are one of the animals in Africa that most game viewers set out to see, yet somehow the life cycle of the humble rhino bot fly has gone on largely undetected for so many years.