Mar. 1, 1925 
Distribution of the Alfalfa Weevil 
485 
minimum of rainfall is not so strongly 
marked. The limiting factors appear 
to be summer rainfall, which averages 
about 7.6 inches, and winter tempera¬ 
tures. The mean annual minimum 
temperature is —23° F., and the five 
winter months average below the freez¬ 
ing point. The growing season is about 
165 days. The spring is slow, so that 
feeding is distributed over a long 
period. 
Astrachan. —The climograph for 
Astrachan is shown in Figure 5. The 
climate is warmer than that of Moscow, 
of Tiflis and Erivan, and their climo- 
graphs are reproduced in Figures 6 
and 7. Tiflis has warmer winters than 
Erivan, but Erivan has drier summers. 
The limiting condition at Tiflis is appar¬ 
ently the precipitation in the spring 
months, May, especially, being favor¬ 
able to fungous enemies. At Erivan 
summer conditions approach more 
closely to those of the Mediterranean 
region, but the winters are cold. 
No data are available regarding mini¬ 
mum temperatures at Erivan, but the 
absolute minimum at Tiflis is 1° F., 
Fig. 5.—Climograph for Astrachan, Russia 
and the rainfall at all times is very and the winter months at Erivan 
light, so that the limiting factor in this average 10° F. colder than at Tiflis, so 
case must be winter temperature, that subzero temperatures must- be 
The mean annual minimum is —13° F., fairly common. Of the two regions, 
and what little snowfall there is must that around Erivan approaches the 
be swept away by the winds, so that rainfall optimum, whereas Tiflis pre- 
the weevils are kept down by the cold sents a limiting condition of rainfall, 
winters. Spring and summer con- _ 
ditions of temperature and precipi- Summary of the Climatic Relations 
tation are close to the optimum, being of Phytonomus Posticus in the 
warm and dry. Old \\ orld 
Transcaucasia. —This is a mountain . . 
region of extremely varied climate. The climatic requirements of the 
Data are available from the two stations alfalfa weevil in the Old World will 
