122 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
perature correlation is valueless unless proper corrections are applied 
for the effects of humidity and light or other important factors as were 
originally suggested by Dr. Shelford. 
Since it was impossible to conduct the detailed experiments upon the 
humidity effects, the study of the insect in its original home was stressed. 
The hythergraph method of Griffith Taylor, (reviewed in the August 
Number of the Geog. Rev. 1919) was used for comparing the foreign 
localities, from which seasonal history records could be obtained, with 
localities in the United States. Briefly this method consists of plotting 
two factors of the climate for each month of the year using normal 
monthly means. The foreign localities were grouped according to 
seasonal history and climatic features and the groups analyzed by 
means of interrelated examinations. From this study certain hypotheses 
concerning the one and two generation types of climate were obtained 
and these limits used in predicting possible seasonal history for localities 
Fig. 3.—'Showing type of graph used for studying seasonal history groups in the 
native home of the Corn Borer and for comparative work with the possibilities of 
adaptation in the new regions of spread. 
in the United States. Chart I shows the type of graph used for com¬ 
parative work as well as typical one and two generation types of climate 
found in the temperate zone. The bad years, i. e., seasons in which 
there occurred intense damage by the corn borer, were also surveyed for 
their climatic peculiarities, and in this manner knowledge was obtained 
concerning the potentiality of the insect in various types of climate. 
