NO. I 



BLACK FLIES OF GUATEMALA — DALMAT 



30s 



Department of Solola 



Simulium ochraceum has consistently been considered the principal 

 vector of onchocerciasis in the Western Hemisphere, not only because 

 of its predominantly anthropophilic tendencies, but because of its dis- 

 tribution in relation to that of the disease. Most epidemiological re- 

 ports on onchocerciasis claim that the distribution of S. ochraceum 

 coincides with that of onchocerciasis. It would follow that the species 

 does not exist, or is only infrequently found, outside of the onchocer- 

 ciasis zones. However, the presence of this species outside of the 

 disease zones, as well as the distribution of other anthropophilic spe- 

 cies, rarely is mentioned. Torres Muiioz (1951), representing Mexico 

 at the First International Conference on Onchocerciasis, expressed the 

 common viewpoint that S. ochraceum is the important vector of oncho- 

 cerciasis by virtue of its distribution, which conforms to that of the 

 disease. 



A study of map 4 will show that ^. ochraceum is widely distributed 

 in Guatemala, outside of the onchocerciasis zones as well as inside of 

 them. As stated under the heading "Animal Associations" in the 

 section on epidemiology, there are some regions in the onchocerciasis 

 zones (Huehuetenango) where 6". ochraceum, has not been found and 

 S. veracrusanum is the dominant anthropophilic species. It will be 

 noted on map 5 that 5. metallicum has a distribution similar to that 



