NEW MUSCOID FLIES FROM THE ANDEAN MONTANYA 145 



in the north and the latter nearer the center of the Peruvian coast strip 

 considerably north of Lima. SuUana, in the Rio Chira valley, is well 

 removed from the western Andean foothills ; but Casma, in the Rio Casma 

 valley, while practically on the coast, is also close up against the bare 

 western spurs of the Andes. The atmospheric humidity in the Rio Chira 

 region is much less than that in the Rio Casma region and prevails dur- 

 ing a less extended season of the year, the maximum of humidity in both 

 being from June to September. This subarid coast strip of Peru shows 

 a northward extension of the Chilean fauna and is almost entirely distinct 

 faunistically from the humid region on the east side of the Andes termed 

 the montanya. In the north only is there a slight intermingling of humid 

 tropical forms acquired from the moist coast region of Ecuador and from 

 the patches of montanya in the valleys and on the moisture-favored slopes 

 of the north Peruvian and south Ecuadorian region where the Andes 

 spread out and their crests become much lower them in the center eind 

 south of Peru. 



The word montanya is the anglicized form of the Spzuiish word mon- 

 tcina, which literally means a mountain area, but has come to signify any 

 area densely overgrown v\dth native vegetation, and especijJly forest 

 growth. The term is here used to mean any humid mountain area from 

 base to top, thus any hunnid area subjected to mountzun conditions. The 

 montanya occurs in its most accentuated phase on the lower half of the 

 east slopes of the Andes. Its lower eastern limits are indefinite in the 

 Spanish-American sense, but may be taken in a biogeographical sense in 

 the Andean region as near the 1 , 000-foot contour line or about the head 

 of steam navigation on the inlcind waterways. It thus includes the belt 

 of considerable fall as indicated by swift-flowing rivers. The term is a 

 very convenient one for use in biogeographic treatment, and while dis- 

 tinctively South American in current geographical application is here in- 

 tended to apply to similar areas elsewhere. The montanya divides eeisily 

 into an upper and a lower belt, the high or dilute montanya and the low 

 or true montemya, the division being generally marked in the Andeain 

 region by the limits of forest growth. In Central America and tropical 

 Mexico the division is marked by the limits of hardwood forest. The 

 line of separation follows practically the same isotherm throughout, for in 

 the Andean region pines are absent and the forest is cJl hardwood. This 

 isotherm is found at about 6,500 to 7,000 feet in latitude 12** S., and 

 gradually ascends northward to 7,500 or 8,000 feet in latitude 4** S. 



