28 DISTRIBUTION AND DISPERSION OF LfiPTINOTARSA. 



taining a repetition of the same sad story." We learn from this data that 

 it required four years in which to disperse generally over the State of Iowa, 

 to become well adapted to its habitat, and to increase sufficiently in numbers 

 to be at the end of that time a dangerous foe to agriculture. In this year 

 we have the first records from Calloway and Putnam Counties, Missouri, of 

 the beginning of a southward advance. Neither record is of first introduc- 

 tion, because the beetle had been abundant for some years in the neighboring 

 counties in Iowa. The record in Calloway County, Missouri, which is one 

 of first ravages, marks the beginning of the southward extension along the 

 Missouri-Mississippi Valley. It is probable that a large portion of the State 

 of Missouri north of the Missouri River was quite as generally inhabited by 

 the beetles as was Iowa. 



In Wisconsin, the editor of the Wisconsin Farmer (April 13, 1S67) states 

 that the beetle was abundant in the St. Croix River Valley in 1865, and 

 that it existed in small numbers in Marquette County in the same year. 

 It was also reported by Priest, from Mosinee, Marathon Count}', Wisconsin, 

 1865, where it did great damage to the potato crop. No specimens from 

 either locality were seen by entomologists. Walsh ( 1 8b6i>), for reasons which 

 he does not state, doubts the accuracy of the Mosinee record, but accepts 

 the statement of the editor of the Wisconsin Farmer, which is based upon 

 less certain evidence. In Illinois, at Mount Carroll, it was found in large 

 numbers ("swarms," Shimer, 1865; Walsh, 1865). At Warsaw, Rock 

 Island, and Alton it was abundant and did much damage to potatoes and 

 egg-plants. It was reported by Riley near Chicago in small numbers 

 (Walsh). 



For the first time in the history of the advance of this beetle the records of 

 the year are sufficiently complete to enable one to draw the eastern boundary 

 with some degree of exactitude. The front of the distribution begins at 

 the north in the St. Croix River Valley (plate 8), passes in a southeasterly 

 direction across Wisconsin to Marathon County, and onwards in the same 

 direction to the shore of Lake Michigan at Chicago. From Chicago the line 

 runs almost straight in a southwesterly direction through Alton, Illinois, on 

 the Mississippi River, and across eastern Missouri to the Missouri River, 

 which it follows to the region of Kansas City, Kansas, and then runs north- 

 ward across northeastern Kansas. In Wisconsin, Iowa, and Illinois the 

 distribution of the beetle west of this line was general, while in Missouri 

 and Kansas it was still local in character. 



Walsh ( 1 865) , calling attention to the rate of advance of this insect during 

 six years, says: "From Omaha, Nebraska, to Rock Island, Illinois, is over 

 360 miles. If the above statement is correct (Hazen), the insect has traveled 

 360 miles in six years, at the rate of 60 miles a year. At this rate it will 

 reach the Atlantic in fourteen years" (*. e. , 1879). 



