NO. I BLACK FLIES OF GUATEMALA — DALMAT 9 



one-third of the entire area of Guatemala but is very sparsely popu- 

 lated. The Sierra Madre, as it crosses the boundary between Mexico 

 and Guatemala, has branching from it a large secondary chain of 

 mountains which extends to the north. The principal cordillera, con- 

 sidered by some to be a continuation of the Andes, forms the volcanic 

 mountains (23 volcanoes included) mentioned above, which extend 

 across the southern part of Guatemala in a general southeasterly 

 direction, dividing the country more or less into two parts ; the north- 

 ern branch of mountains, which runs in a general west to east direc- 

 tion, is comprised of the Sierra de los Cuchumatanes, Sierra de Chua- 

 cus, Sierra de las Minas, and the Montana del Mico. Also branching 

 from the northern group are the Sierra de la Cruz, which passes to 

 the north of Lake Izabal, somewhat paralleling the Montana del Mico, 

 and the Sierra de Chama, which runs northward from the Sierra de 

 Chuacus. The Sierra del Merendon, another small secondary range 

 that branches from the volcanic cordillera, runs along the eastern 

 limit of Guatemala, bordering Honduras. 



Guatemala, with its complex topography and great range of alti- 

 tudes has, as would be expected, a correspondingly great diversity in 

 climate, and the changes are often very abrupt. The country is suffi- 

 ciently far north of the Equator for the temperature to show some 

 seasonal variation at any given altitude. During the winter months of 

 the north temperate regions, the average monthly temperature in 

 Guatemala also drops. This is best exemplified by a small but notice- 

 able drop in minimum temperature in the highlands of Guatemala 

 during December, January, and February. This fall in temperature, 

 however, is hardly perceptible in the lowlands. Because of these slight 

 variations, the seasons in Guatemala are often referred to as the "hot 

 season" (March to October) and the "cool season" (November to 

 February). Actually, however, in any one area the average daily tem- 

 perature varies but little throughout the year, and the daily maxima 

 and minima do not significantly vary from the mean daily tempera- 

 tures. The well-marked variations in temperature really arise between 

 zones of different altitudes. These zones have been termed "tierra 

 caliente" (hot region) for the coastal plain (sea level to 2,000 feet) ; 

 "tierra templada" (temperate region) for the foothills (2,000 to 6,500 

 feet) ; and "tierra fria" (cold region) for the mountains (6,500 feet 

 and above). 



It will be seen from table i that as the altitude increases the mean 

 annual temperature decreases, and the difference between the mean 

 annual maximum and minimum increases. 



With the exception of relatively slight variations in temperature 



