than the rest of the body. The elongat- 

 ed wings are brown to black and, when 

 the fly is at rest, run along almost the 

 entire length of the body [see photograph 

 on opposite page]. Adult flies occur in 

 parts of Africa where their rhinoceros 

 hosts live. In recent years that has meant 

 the grasslands and savannas of southern 

 and East Africa, but historically the flies 

 and their hosts extended, except for the 

 Congo Basin, across most of sub-Saha- 

 ran Africa. No matter the flies' range, 

 even the most experienced collectors 

 have had a tough time finding them. 



Two other bot-fly species of the 

 genus Gyrostigma are known, and both 

 are exceptionally rare. One of them, 

 G. conjungens, was discovered in its bot 

 form in the belly of a Kenyan black rhi- 

 noceros in 1901 , but it hasn't been col- 

 lected, or even seen again, since 1961. 

 The other rare species, G. sumatrensis, 

 is known only from a single bot, which 

 was in the late developmental stage of 

 the larva known as the third instar. It 

 was discovered in a captive Sumatran 

 rhinoceros and described in 1884, but 

 it, too, has not been seen again. No 

 Gyrostigma bot flies have been found in 

 the Indian or the Javan rhinos, but it is 

 not unreasonable to expect that the 

 intestinal parasites may eventually be 

 discovered in all five rhino- 

 ceros species. 



In 1 847 the French naturalist and ex- 

 plorer Adulphe Delegorgue de- 

 scribed large numbers of bots in the 

 stomach of a black rhinoceros from 

 northeastern South Africa. He pub- 

 lished this vivid description of them in 

 his Voyage dans I'Afrique australe ("Trav- 

 els in Southern Africa"): 



The Rhinoceros Africanus bicomis could well 

 claim the title of foster father of bots. The 

 imagination boggles at the quantity con- 

 tained in his stomach; they could be shov- 

 eled out in bushels. ... I am much inclined 

 to think that the viciousness and ill-humor 

 which characterize the Rhinoceros Africanus 

 bicomis are due simply to the presence of 

 thousands ot these parasites and can be com- 

 pared with the irritability of a man infested 

 with tapeworm. However, in spite of then- 

 numbers, which sometimes seem to exceed 

 all natural limits, bots do not, as far as I know, 

 cause the death of indigenous animals. 



Delegorgue was the first of many to 

 become intrigued with the biology of 

 G. rhinocerontis. Brian R. Stuckenberg, 

 an African fly specialist who is also a 

 former director of South Africa's Na- 

 tal Museum, maintained an interest in 

 Gyrostigma biology throughout his 

 fitty-year career, continuing South 

 Africa's tradition as the hub of research 

 on African bot flies. Stuckenberg took 

 the first of what are still only a few good 

 photographs of living bots [see photo- 

 graph at top of this page]. He and other 

 entomologists working today, includ- 

 ing myself, rely heavily on the pio- 

 neering studies of another famous fly 

 taxonomist, Fritz K.E. Zumpt, who 

 was based in South Africa and pub- 

 lished his major works during the 

 1950s and 1960s. 



What about the fly's behavior? Ob- 

 serving the flies in the field has been 

 difficult. Many of the South African 

 specimens studied by Zumpt and oth- 

 ers were not wild; rather, they were 

 reared from mature bots collected from 

 the stomachs of dead hosts. Finding 

 mature bots hasn't been easy, and get- 

 ting mature flies to lay eggs has been 

 even harder. Only a few large museum 

 collections have the luxury ot owning 

 an adult specimen of G. rhinocerontis, 

 and amateur collectors luckv enough 



Stomach wall of a rhinoceros has become 

 pitted from the depredations of bot-fly larvae, 

 which parasitically feed on the rhino tissue. 

 The three larvae in the photograph, shown 

 actual size, are nearly ready to leave the rhino 

 gut, pupate, and emerge as adult flies. 



to have caught the elusive insect prize 

 their specimen highly. 



What makes the adult flies so hard 

 to collect in the field? First, the 

 airborne stage of their lives lasts only 

 three to five days, severely limiting the 

 collecting time. One reason the air- 

 borne stage is so short is that Gyrostigma 

 flies have rudimentary, nonfunctional 

 mouthparts; in fact, they probably don't 

 feed at all during that stage. Even 

 though they gorge themselves as larvae, 

 stored energy goes quickly when you're 

 flying but not eating. That could cer- 

 tainly account for their speedy demise. 



A second reason the flies are hard to 

 catch is that they probably do not fly ex- 

 tensively by day. The evidence is con- 

 flicting about when the adults are most 

 active, and no one knows where they 

 spend their time when they are neither 

 flying nor laying eggs. Some observers 

 have reported them flying near their rhi- 

 noceros hosts on hot, sunny days in 

 northern KwaZulu-Natal, a province in 

 eastern South Africa. But some ento- 

 mologists think they are crepuscular, be- 

 coming active only at dawn or at dusk. 



One explanation for the seeming 

 contradiction may be that the two sex- 

 es keep to diff ering schedules. I believe 

 that the female flies will prove to be 

 most active during daylight hours, 

 when they deposit their eggs on the 

 hide of their hosts, and that the males 

 are most active at dawn and dusk, w hen 

 mating may take place. I have exam- 

 ined the specimens in the Natal Mu- 

 seum's collection — the largest fly col- 

 lection in Africa — and all of our field- 

 collected male flies w ere found at dusk. 



June 2006 NATL' It. A l iiimors. 



19 



