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THE HORSE-RADISH FLEA-BEETLE. 
~I 
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, Il., being the most 
southerly locality from which it has been reported. 
Until otherwise 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).*| 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. 
