Conditions 



35 



are of great length. At Gatun many flow from 

 the hills toward the settled area. During many 

 rainy periods, when all the soil is well water- 

 soaked, the hillside streams give least trouble, as 

 the larvas are washed out of them. Unfortunately 



' Sosa records compared wlih jVncon. ' June. 



Note.— Elevation of Ancon anemometer 69 feet above grounij and appro3dmateIy 160 feet above mean 

 eealevei. Sosa anemometer 25 feet above ground, and approximately 220 loet above mean sea level. 



these hillside streams are often transporters of 

 larvffi and pupse, and become an important source 

 of mosquitoes when they reach a lower grade, or 

 enter larger streams or rivers near a settlement. 



During dry periods streams become prolific 

 sources of mosquitoes; and even after the stream 

 becomes dry many depressions still contain water 

 in which larvae rapidly develop. As the rain- 

 fall is heavy, there is a rapid rumi off, and erosion 



