The se­cret life of the rhino bot fly

go! - - Upfront In Brief -

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.

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