Examination of 253 samples of bunch grass, collected in 47 Iowa counties during Mar. 1935, showed that the mortality of the chinch bugs hibernating in the grass varied from as low as 20% in Clinton County to as high as 88% in Story and Dallas Counties. Areas of low, medium and high mortality were fairly well defined; attempts to show a relationship between the mortality and such weather records as minimum temp. and mean monthly precipitation failed. The mean depth of snow and the amt. of protection afforded (insulation) by the grass or mulch cover are important factors in influencing mortality. An apparent correlation between the amt. of precipitation (as rain) occurring Jan. 16 to 19, and percentage of dead bugs was observed.[long dash]In general, certain combinations of .specific ecological conditions may be correlated with chinch bug mortality but monthly means or other summarizations tend to conceal these relationships.