PAPERS ON ZOOLOGY 



267 



Fig. 5. Showing parallel curves for health, school attendance in 

 eastern United States, death-rate in Chicago and chinch bug infesta- 

 tion in Illinois from ISSO to 1910. Curve A (scale at left) normal 

 health of the general population is shown at OTc while bad health is 

 indicated by per cent below and good health by per cent above. 

 Curve B (scale at right) shows the parallel of school attendance to 

 health. Curve C (scale at right) shows the death-rate in Chicago. 

 Normal death-rate is indicated by zero per cent, high death-rate by 

 per cent above and low death-rate by per cent below. Curve D (orig- 

 inal; scale at left) shows relative chinch bug infestation in Illinois from 

 records in the state entomologist's office. The records show three de- 

 grees of damage, slight, moderate and severe, by counties. Slight was 

 given a value of 1, moderate 2, and severe 3; these figures were multi- 

 plied by the number of counties in each case, and then totaled, and 

 then divided by two for convenience in plotting. There is a good 

 correspondence between chinch bug damage and death-rate in Chi- 

 cago; the entire state of Illinois would be better. 



