Mar. 1, 1925 
Distribution of the Alfalfa Weevil 
483 
the weevils would not be forced into 
inactivity by the heat of summer, the 
generations would be more or less 
spread out, and the feeding would con¬ 
tinue through a larger portion of the 
year but be less concentrated and 
therefore less destructive. . . . Mr. 
H. S. Smith, who studied the insect in 
Italy, was of the opinion that that was 
one of the principal factors in producing 
the condition in Italy along the sea- 
coast, where the weevil is always 
present in considerable numbers, but 
is of no consequence as a pest. Its 
feeding is distributed through many 
months instead of a few weeks .” 
Summarizing the above information: 
The alfalfa weevil is at times a major 
pest in southern France, Italy, and 
Turkestan; a minor pest in Germany, 
Sweden, Denmark, southern Russia, 
and Transcaucasia. If that gives an 
approximate picture of the economic 
distribution of this species, the climatic 
optima are found in the Mediterranean 
region and Turkestan and the limiting 
conditions farther north, in Germany, 
Sweden, Denmark, and southern Russia, 
with a limiting condition of a similar 
nature in Transcaucasia. 
Climatic Conditions 
The writer has spent considerable 
time collecting and comparing the 
climatic data for the various regions 
listed above, and is greatly indebted to 
C. F. Talman, librarian of the United 
States Weather Bureau at Washington, 
for securing data and for other services 
in this connection. The basic data 
have been taken from Hann (8) and 
Kendrew (4 ), and it is impracticable to 
cite specific references for each quota¬ 
tion. The climatic data have been 
very carefully studied, and no attempt 
is made to give those for any given 
station in full, such a citation being 
replaced by a summary of the import¬ 
ant conditions of a general region as 
shown by a study of several stations. 
have essentially similar climates, so 
that the region may be treated as a 
unit. The important factors in this 
study are (1) the warm, wet winters, no 
month having a mean temperature 
below freezing, and (2) the hot, dry 
summers, seven to nine months being 
above 50° F. and five to six months 
above 60° F. in mean temperature. 
The spring from April to July is 
increasingly dry, March and April 
being the only months favorable for 
fungous growth. The precipitation of 
the three summer months—June, July, 
SO' 
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Fig. 1 .— Climograph for Marseilles, France 
Optimum Conditions 
Mediterranean region. —The 
general character of the annual cycle 
of temperature and precipitation is 
well shown in the climograph for 
Marseilles, France (fig. 1). The climo¬ 
graph of Ball is a graph on which 
monthly means of temperature are 
plotted against monthly totals of pre¬ 
cipitation. The points are joined in 
chronological order, so that a picture 
of the annual cycle of temperature and 
rainfall is obtained. All. the stations 
studied in southern France and Italy 
and August—ranges from 23^ to 4 
inches for the period, averaging very 
close to 3 inches. The mean relative 
humidity in summer ranges from 50 to 
65 per cent, and all times of the year 
are very sunny, most of the winter rain¬ 
fall .coming in heavy showers, followed 
by bright sunshine. 
Turkestan. —The attacks of the 
weevil in this region have been most 
severe in the Valley of Ferghana. 
This is an irrigated valley in the 
mountains of the southern part of 
the province, which has climatic con¬ 
ditions very comparable to those of 
