12 



MONTANA EXPERIMENT STATION BULLETIN 216 



charge of control operations was swamped with work and could 

 not begin to oil all of the irrigation water that contained 

 mosquito larvae. As a consequence, although dead mosquito 

 larvae were so thick in many fields as to create a strong stench, 

 enough of them matured to produce a heavy crop of mosquitoes 

 in June. Then came the rains in July, the total precipitation 

 being 5.17 inches as compared with the normal rainfall of 

 1.73. Two and four-tenths inches of the July rainfall came in 

 two hours' time, which produced more or less of a flood. This 



Figure 2 



high water distributed the mosquito larvae, that were at that 

 time in pools and irrigated fields, all over the country, so that 

 mosquitoes were maturing out of road-side pools, drainage 

 ditches, and almost every place where standing water was 

 found. Needless to say, there was much more water contain- 

 ing mosquito larvae than could be oiled by one man or by the 

 quantity of oil available. The accompanying chart (fig. 2) 

 graphically shows the abnormal conditions under which this 



