6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



and February 1948, that the members of the family of the plantation 

 owner bound their arms and legs with gauze in an attempt to keep 

 the swellings down and to prevent further secondary infections. Their 

 faces were so swollen that their eyes were almost completely obscured. 

 They finally had to leave the plantation until the fly population sub- 

 sided. In this case the flies were breeding on the finca. Since the 

 homes of the affected individuals were surrounded by hills that formed 

 a natural bowl, the winds, instead of carrying flies into the area, were 

 preventing their exit from the hollow. Because at that time no insecti- 

 cides were available, it was finally necessary for the people to leave 

 the plantation until the fly population subsided naturally. 



TRANSMISSION OF DISEASE 



The Simuliidae are important not only because of their effect, as 

 pests, upon man and other animals, but also as vectors or intermediate 

 hosts of pathogenic organisms. Simulium species have been shown 

 to transmit Leucocytosoon smithi of turkeys (Skidmore, 1932; John- 

 son, Underbill, Cox, and Threlkeld, 1938), Leucocytosoon anatis of 

 ducks (O'Roke, 1934), Onchocerca gutturosa of cattle (Steward, 

 1937), and Onchocerca volvulus of man (Blacklock, I926a,b). Mem- 

 bers of this family have also been incriminated in the transmission of 

 Setaria equina of horses, and Parker (1934) was able to transmit 

 tularemia by the interrupted feedings of Simulium decorum katmai 

 Dyar and Shannon. As stated in the introduction, human onchocer- 

 ciasis, transmitted by several species of Simuliidae, is now known 

 to be endemic throughout extensive regions of Equatorial Africa and 

 in South America (Venezuela), Central America (Guatemala), and 

 southern Mexico. The present study of the Simuliidae has been made 

 in an attempt to help establish their role in the transmission of human 

 onchocerciasis in Guatemala and to obtain sufficient data concerning 

 their biology and ecology to permit the establishment of an efficient 

 control program against them. 



EPIDEMIOLOGY 



Presence and spread of onchocerciasis in Guatemala and 

 Mexico. — Various investigators have postulated that onchocerciasis 

 was introduced into Guatemala and Mexico by infected Negro slaves 

 brought in from Africa ; also that the disease spread from Guatemala 

 to Mexico owing to large movements of population such as religious 

 pilgrimages and migrations of field workers. These assumptions have 

 been based primarily on the fact that the disease was recognized in 

 Guatemala (1915) prior to its discovery in Mexico (Fiilleborn, 1923). 



