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JOURNAL OF ECONO^IIC ENTOMOLOGY 



\yoi. g 



Figure 10 — Showing the distribution of vegetation in North America before it was 

 put under agricuhural conditions. The shaded "prairie" area may be regarded as 

 the original center of abundance of agricultural pest species. 



of species taken by the writer on the margins of ponds and lakes such 

 as are shown in Plate 7, figure 1, we find that one third of the phyto- 

 phaga listed are mentioned by one or both of these authors. A com- 

 parison of lists of species taken from the margins of sandy depressions 

 such as occur about the lakes and larger rivers and we find again roughly 

 one-third of the species mentioned by one or both of these authors. 



