PINK BOLLWORM OF COTTON" IN MEXICO. 
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 
1916 
1917 
1918 
11.42 
4.63 
4.30 
3.46 
7.14 
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 
1919 
C 1 ) 
0) 
0.35 
Trace. 
0.02 
2.76 
Trace. 
1.56 
0.07 
0.09 
1.74 
0.21 
1.20 
Trace 
0.54 
April 
0.00 
0.00 
1.44 
July 
3.98 
5.16 
1.75 
0.87 
0.15 
2 0.00 
Total 
6.80 
15. 09 
No record. 
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 
