PINK BOLLWORM OF COTTON IN MEXICO. 3 



were reached. The relative humidity is rather high, often reaching 

 the saturation point at night. 



From monthly records kept by the Tlahualilo Co., at Tlahualilo, 

 Durango, covering a period of 15 years extending from 1904 to 1918, 

 inclusive, the average rainfall for that region has been 8.07 inches 

 per year. 



Table I. — Annual precipitation in inches at Tlahualilo. 



Year. 



Precipi- 

 tation. 



Year. 



Precipi- 

 tation. 



Year. 



Precipi- 

 tation. 



1904 



19C5 



1906 



1907 



1908 



6.09 

 11.31 

 12.09 

 8.71 

 6.43 



1909 



1910 



1911 



1912 



1913 



13.32 

 3.91 



6.98 

 8.56 

 12.79 



1914 



1915 



11.42 

 4.63 

 4.30 

 3.46 

 7.14 



1916 



1917 



1918 



From records taken at the laboratory in Ciudad Lerdo, the fol- 

 lowing figures are given, covering the years 1918 and 1919, the years 

 during which the observations relating to the pink bollworm in this 

 report were made. 



Table II. — Monthly precipitation in inches at Ciudad Lerdo, Durango. 



Month. 



Precipitation. 



1918 



January. . . 

 February.. 



March 



April 



May 



June 



July 



August 



September. 



October 



November . 

 December. 



Total 



C 1 ) 



C 1 ) 

 0.35 



Trace. 

 0.02 

 2.76 



Trace. 

 1.56 

 0.07 

 0.09 

 1.74 

 0.21 



1.20 

 Trace 

 0.54 

 0.00 

 0.00 

 1.44 

 3.98 

 5.16 

 1.75 

 0.87 

 0.15 

 2 0.00 



15.09 



2 Record only for Dec. 1-10. 



CULTURAL METHODS AND PRODUCTION. 



This section is semiarid and depends upon the water from the Rio 

 Nazas and Rio Agua Naval for irrigation. The water usually comes 

 down some time between August and December and is applied at a 

 rate which is equivalent to about 1 meter deep to the fields that are to 

 be planted in the following year. With an occasional rain in June 

 or July or a small amount of water from the river during these 

 months the fall irrigation suffices for the crop. As there is not 

 enough water for all the land, only a small portion is cultivated, and 

 on some plantations a portion of the land regularly lies fallow for 

 several years at a time. Under this system of cultivation the land 



