OF WASHINGTON. 73 



tained for eight or ten years, until the host plant was destroyed. 

 These examples and others show that fairly fixed food races 

 are developed. 



Mr. Webster agreed with Mr. Marlatt, and mentioned the 

 northern corn root-worm (Diabrotica longicornis Say) as an- 

 other illustration of an insect changing its food habits. There 

 is no doubt whatever that this species long ago inhabited the 

 country between Kansas and Nebraska and the Atlantic Coast, 

 but back in the seventies the beetle was by no means common 

 in many parts of Illinois and eastward. Mr. Webster remem- 

 bered perfectly the first specimen he ever found, about 1875, 

 in northern Illinois. It was afterwards found near Buffalo, 

 N. Y., on willows, by Reinecke, and in Nova Scotia by Har- 

 rington. Up to about 1860 Illinois and Iowa were essentially 

 wheat-growing States and corn was a minor crop. Soon after 

 that, conditions began to change, the wheat fields were diverted 

 to corn, and this crop was grown year after year successively 

 on the same land. It must have been some time between 1870 

 and 1880 that the species began to infest the corn fields, and 

 the first records we have of its destructive work on corn came 

 from the great corn-growing regions of Illinois and eastern 

 Iowa. Very soon afterwards the insect began to swarm in 

 the corn fields and the crop in some localities was badly dam- 

 aged and even wholly destroyed. Now this corn- feeding race, 

 if it may be so termed, began to diffuse itself to the eastward. 

 By 1885 it had become a serious enemy to corn in western 

 Indiana and by 1892 it had reached western Ohio ; by 1895 ^ 

 had extended its ravages nearly half way across the State. Its 

 progress during these years in Ohio was illustrated by maps 

 in Bulletin 68 of the Ohio Agricultural Experiment Station. 

 In contrast with this condition in the western part of the 

 State, it may be stated that it was impossible to find it far 

 in advance of its destruction either as to locality or date. At 

 Wooster, in the northeastern-central part of the State, Mr. 

 Webster was unable to find it at all until 1902, when a single 

 beetle was found upon the blossom of a garden sunflower. 

 Now, its occurrence sparingly over this whole country long 

 prior to these days is beyond question, and not until this corn- 



