NO. I BLACK FLIES OF GUATEMALA — DALMAT 39 



tocerca could be found and none showed development. Bequaert 

 (1929), working in Liberia, found developmental forms of O. vol- 

 vulus larvae in a number of black flies, which he identified as 6^. dam- 

 nosum. These findings of Sharp and Bequaert certainly help confirm 

 the conclusion of Blacklock that S. damnosimi is at least one of the 

 vectors of O. volvulus in Africa. 



Hofifmann (i930a,b,c,d,e; 1931a), working in Mexico, traced the 

 path and development of the larvae of 0. volvulus in .S". callidum Dyar 

 and Shannon, vS'. ochraceum Walker, and 5^. metallicum Bellardi, using 

 wild-caught flies. From his observations he concluded that the larvae 

 of 0. volvulus can completely develop in S. callidum and in 6'. metalli- 

 cum but not in 5". ochraceum. Strong (i93ia,b,c ; et al., 1934), work- 

 ing in Guatemala, demonstrated that 5". ochraceum, metallicum, and 

 callidum were concerned in the transmission of onchocerciasis, and he 

 also described a further (infective) stage in the development of the 

 larva, thereby completing the entire cycle in the fly. 



De Leon (i94oa,b) reported having found various developmental 

 stages of the larvae in wild-caught S. metallicum, ochraceum, and 

 callidum in Guatemala. In 1947 he reported the tracing of the develop- 

 ment of the larva in 5. callidum through 130 hours. He was unable to 

 maintain the other two principal anthropophilic species of Simulium in 

 captivity for more than 3 days. De Leon charted his results of dissec- 

 tions of wild-caught flies to show the percent of natural infection with 

 larvae of O. volvulus. In the month of December (cofifee harvest and 

 period of cofifee processing when laborers are most exposed to bites 

 of the flies) he found 0.89 percent of 433 6". ochraceum infected and 

 1.86 percent of 631 5. metallicum infected on various fincas of the 

 Yepocapa onchocerciasis zone. 



Wanson, Henrard, and Peel (1946), working in the Belgian Congo, 

 were the first to report the entire development of O. volvulus in 

 laboratory-reared flies (S. damnosum) . Like Blacklock (1926b), they 

 found that the microfilariae reached the infective stage in only 6 to 7 

 days. 



Vargas (1948), in Mexico, was able to infect one laboratory-reared 

 S. mangaheirai with microfilariae of O. volvulus. After 124 hours he 

 killed the fly, sectioned it, and found several "sausage"-stage larvae 

 in the thorax. In 1949 Vargas and Ruiz Reyes reported two wild 

 specimens of 6^. exiguum from Oaxaca, Mexico, infected with "sau- 

 sage" forms which they believed to be 0. volvulus. 



In Guatemala, Gibson (1951a), using wild-caught flies fed on in- 

 fected individuals, traced the development of 0. volvulus in 6^. metalli- 

 cum up to 166 hours ; in 5". callidum up to 176 hours, and in 5". ochra- 



