THE HORSE-KADISH FLEA-BEETLE. 7 



examples, notably the Colorado potato beetle, of an insect pest which 

 has first traveled eastward. 



The predictions made in 1896 that the horse-radish flea-beetle 

 probably would spread soon to southern Minnesota and Michigan 

 were practically correct, as the species is known to be near the State 

 line of Minnesota in Iowa. It had reached Michigan by 1915 and 

 had spread to Ohio and Nebraska the same year. That it would take 

 an eastward sweep as far as Potsdam, N. Y., Quebec, Canada, and 

 northern New Jersey was scarcely expected for years to come. It is 

 now near the border line of Pennsylvania and will undoubtedly 

 spread to that State and to southern New York. The tendency is 

 northward rather than southward, Bloomington, 111., being the most 

 southerly locality from which it has been reported. 



Until other wise known (and there is little likelihood of learning 

 anything more definite with regard to the first appearance of the 

 horse-radish flea-beetle), it must be concluded that this species was 

 introduced first into Illinois in or around Chicago. From this center 

 it has spread westward and northward, and has evidently taken large 

 commercial jumps eastward, or has been introduced into New Jersey 

 independently, but has made little progress to the south. From pres- 

 ent knowledge it apparently prefers the regions about the Great 

 Lakes, but in time doubtless it will be quite as numerous in other 

 waterways and tributaries, even in moist places generally, which are 

 the natural habitat of its principal food plants — horse-radish and 

 marsh cress. In the course of time the somewhat scant records 

 doubtless will be greatly enlarged, showing thereby a more general 

 distribution than is known at present. It has been remarked that 

 in Wisconsin, in the Green Bay region, conditions for the develop- 

 ment of this species are highly favorable. This is in the northern 

 portion of the Transition Life Zone, while Quebec is in the Canadian 

 portion of the Boreal Zone. 



REVIEW OF LITERATURE. 



An account of the horse-radish flea-beetle was given by the senior 

 author in 1895, which is now out of print (3). 1 In this article men- 

 tion was made of the first occurrence of the species in this country 

 and of the European literature, and the insect was compared with 

 other species of its genus. The original technical description was 

 published in 1803 (1). In 1893 Julius Weise (2) gave a systematic 

 and detailed description of the species with biologic notes and 

 bibliography. In 1897 (4) the senior author noted the occurrence of 

 this insect in Wisconsin in 1896 and suggested the probable range 



1 Figures in parentheses refer to Bibliography, p. 15. 



