In our continuing series on weird flies, here’s a corker. At about 1.5 inches long, it’s Africa’s largest fly: Gyrostigma rhinocerontis, the rhinoceros bot fly. It’s highly specialized, laying its eggs only on the head of the white and black rhino. The larvae then burrow into the flesh, where they develop in the rhino’s stomach. When they’re ready for the next life stage, they exit through the rhino’s anus and pupate in the soil.
According to London’s Natural History Museum site,
Despite their large size, adults live only for a few days (3–5 days in captivity) because they have very reduced non-functional mouthparts and do not feed. [You can see the lack of mouthparts in the photo below.]
Within that short life span, female flies have to locate a male, mate and then find a new rhinoceros host for their eggs.
As rhinoceros numbers decline so do the numbers of these flies, and should rhinos become extinct, the flies would probably disappear too, providing an example of co-extinction.
Because the adults are so ephemeral, it’s rare to find one of them, and they’re prized by collectors. To me they look like wasp mimics, which may afford them some protection:
Here’s the parasitic larva:
There’s a lot more on this beast in David Barraclough’s article from Natural History in 2006. e.g.:
In 1847 the French naturalist and explorer Adulphe Delegorgue described large numbers of bots in the stomach of a black rhinoceros from northeastern South Africa. He published this vivid description of them in his Voyage dans l’Afrique australe (“Travels in Southern Africa”):
The Rhinoceros Africanus bicornis could well claim the title of foster father of bots. The imagination boggles at the quantity contained in his stomach; they could be shoveled out in bushels…. I am much inclined to think that the viciousness and ill-humor which characterize the Rhinoceros Africanus bicornis are due simply to the presence of thousands of these parasites and can be compared with the irritability of a man infested with tapeworm. However, in spite of their numbers, which sometimes seem to exceed all natural limits, bots do not, as far as I know, cause the death of indigenous animals.
h/t: Matthew Cobb