NO. I BLACK FLIES OF GUATEMALA — DALMAT 7 



Certainly the disease was already well established in Guatemala when 

 Robles (1919) discovered its presence in 1915. Federico Pola de 

 Torroella (1947), a cartographer with the Pan American Sanitary 

 Bureau when the author began his work in Guatemala, was afforded 

 the opportunity of examining many old titles and other documents 

 relating to land holdings, while in the process of preparing maps. In 

 the title to a coffee plantation in Oaxaca, Mexico, Torroella found 

 mention of the fact that Negroes and Indians working on that planta- 

 tion in the fifteenth century were infected with the disease, charac- 

 terized by nodules on the head and trunk regions, which often led to 

 blindness. Supposedly a Spanish physician was sent from Spain to 

 study the disease. Torroella has been attempting to obtain copies of 

 documents in the Spanish archives to substantiate these statements. 



Whether the disease was introduced from Africa to the Americas, 

 or whether it spread from Guatemala to Mexico, is of academic im- 

 portance only. The fact remains that onchocerciasis, at present, does 

 exist in the Americas (Mexico, Guatemala, and Venezuela), Since 

 it appears to be endemic only in certain circumscribed areas (map i), 

 factors that probably contribute to this phenomenon should be dis- 

 cussed. Some of these are geography, climate, occupation of the 

 people, the people themselves, and environmental factors such as plant 

 associations, animal populations, and streams, 



GEOGRAPHY AND CLIMATE a 



GUATEMALA 



Guatemala is situated between latitude i3°46' and 17° 58' N, and 

 longitude 88° 13' and 92° 12' W, Its land mass, approximately 42,300 

 square miles, faunistically forms a transition between the Neotropical 

 and Holarctic regions. Griscom (1932) recognizes three life zones in 

 Guatemala : The Tropical Zone, from sea level to 3,000-4,500 feet ; 

 the Subtropical Zone, 3,000-6,000 feet and locally much higher ; and 

 the Temperate Zone, 5,000-13,000 feet. It has often been said that 

 Guatemala has more variation in altitude in proportion to surface 

 area, as well as greater diversity of climate, than any other portion of 

 the earth. Moving inland from the Pacific Ocean, certain geographical 

 areas can be distinguished (map 2) : (i) Bordering on the ocean, 

 the coastal plain appears as a 30-50-mile-wide band rising uniformly 

 to an elevation of 1,000-2,000 feet; (2) the foothills of the Sierra 

 Madre, which continue to rise from the coastal plain more rapidly and 

 irregularly to about 5,000-6,000 feet; (3) the volcanic mountains 



3 Shelford, 1926; Griscom, 1932; author's personal observations and data. 



