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IT'S A JUNGLE 

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giving credence to the crepuscular the- 

 ory. But there is no solid information 

 available about where mating takes 

 place — if there were, the flies might be 

 captured or at least observed. 



Finally, the flies are fairly safe from 

 the traps of insect collectors and ento- 

 mologists because even the most dar- 

 ing collector never gets very close to 

 the formidable rhinoceroses for long! 

 In my twenty years of collecting flies in 

 the field, I have managed to catch on- 

 ly one adult Qyrostigma. I was on a re- 



anterior end of the bot \scc photomicro- 

 graph below] . There the bots feed on their 

 hosts' blood and tissue. 



As the bot continues to eat away at 

 the rhino, it progresses through two 

 more stages of development. At the sec- 

 ond instar, it is 0.8 inch long, and has 

 developed more prominent spines. At 

 the third and final instar, it reaches its 

 full adult length, but the most striking 

 feature of the third instar is the devel- 

 opment of large bands of spines. Each 

 band comprises three to four rows of 



Pink bot-fly larvae in an intermediate, or second instar, stage of growth, feed 

 on the stomach wall of a white rhinoceros that has just died (left). The larvae 

 attach themselves with mouth hooks and spines, both visible in the photomi- 

 crograph (right), magnified 20X. 



serve in northern KwaZulu-Natal ear- 

 ly one summer evening, and a male rhi- 

 no fly loudly buzzed up to a light that 

 I had set up in hopes of catching just 

 such a specimen. I knew rhinos were 

 in the area, but I was still surprised and 

 delighted by my good fortune. Flies 

 have been attracted to light traps in oth- 

 er parts of South Africa, as well; they 

 were captured in Kruger National Park 

 soon after rhinoceroses were re-intro- 

 duced there from KwaZulu-Natal. 



The life cycle of the rhinoceros bot 

 fly begins when female flies de- 

 posit oblong-shaped eggs in crevices in 

 the hosts hide, apparently near the rhi- 

 no's horns or elsewhere on the head. 

 Precisely what happens next is un- 

 known; I think it likely that once the 

 eggs hatch, after about six days, the 

 young bots enter the rhino through its 

 mouth or nostrils and eventually attach 

 themselves to the lining of the rhino's 

 stomach wall. They hook into it with 

 spines and a pair of well-developed 

 mouth hooks: sicklelike structures at the 



sharp spines. The spines help the bots 

 attach to the rhino s stomach and bur- 

 row into it, a process that leaves large 

 pits in the stomach wall. No scar tissue 

 seems to result from the pits, though, 

 so they are thought to be benign. 



Unlike their adult forms, the bots of 

 Gyrostigma have often been found in 

 large numbers inside a rhinoceros's 

 stomach. Only once, though, have I 

 had the good fortune of examining 

 them. Parts of a freshly dead rhino, 

 from Pilanesberg National Park, in 

 northern South Africa, were couriered 

 to me in a parcel (I could not get to 

 the site in time for dissection). I found 

 quantities of first- and second-instar 

 bots still attached to the stomach wall 

 of the dead rhino — not "bushels" of 

 them, as Delegorgue described, but 

 certainly fifty or more. 



The bots were clustered in groups. 

 The first instars were colored dark pink 

 and buried deep within the mucosal 

 folds of the stomach lining. The sec- 

 ond instars were larger, a paler shade 

 of pink, and more conspicuous because 



20 



NATUIUI HISTORY June 2006 



