74 The Control of Mosquitoes 



established, about December i, 1913. The month- 

 ly Anopheles catch at this camp was, December, 

 1913, 320; January, 1914, 1969; February, 1914, 

 2834. Recently the Anopheles albimanus is be- 

 coming the predominating species. 



Strange to say until January, 1914, there has 

 been no influx of Anopheles from the lake at Gatun 

 and practically no breeding along the shore of the 

 lake near that town, although within a mile 

 conditions along the lake shore appear quite 

 similar to those near Cano and Gamboa. Condi- 

 tions may change and become favorable at a 

 later date. 



OCCURRENCE OF ANOPHELES IN BRACKISH WATERS 



At Cristobal, Beach Island, in the Rio Grande 

 valley, and at Gatun, Anopheles larvae have been 

 found in brackish and salt water. In the first 

 three locations the propagation areas were affected 

 directly by tide water. At Cristobal, in that 

 part of the tidal flats covered by high tides and by 

 excessive tides, larvae were found to be numerous 

 wherever clearings were made and leaves remained 

 in the water. Clumps of plant stems afforded 

 hiding-places to the larv^ of Anopheles albimanus 

 and Anopheles tarsimaculata, even when small 

 fish were present. Invariably larvae were most 



