BULLETIN" 535, TJ. S. DEPABTMENT OF AGRICULTURE. 



ORIGIN AND DISSEMINATION. 



The horse-radish flea-beetle is of European origin, and was first 

 described by Koch in 1803 x from Germany. It is a well-known 

 species in the Old World, and its specific name is derived from its 

 favorite food plant (Nasturtium) Radicula armoracia. Like all of 

 the striped flea-beetles of the true genus Phyllotreta, the present 

 species breeds on cruciferous plants. 



As to the means of introduction of this species in the heart of this 

 country, it was probably brought in with horse-radish and less prob- 

 ably in marsh cress (Radicula palustris), or possibly with some 

 potted plant. It is not impossible that these plants were brought to 

 America expressly on account of, if not actually for. exhibition at 



Fig. 6. 



-Map showing present known distribution of the horse-radish (tea-beetle. 

 (Original.) 



the Columbian Exposition. It is remarkable, however, in being 

 introduced, not near a seaport, but so far inland. 



In the place of its nativity this species ranges throughout middle 

 Europe. Among early records of its establishment in the United 

 States are Guttenberg, Iowa; Chicago and Bloomington, 111.; and 

 Okauchee, Wis., about 30 miles due west of Milwaukee, and in 1896 

 there was a strong probability that it would soon spread to Missouri 

 and perhaps to southern Minnesota and Michigan — in other words, 

 that it would establish itself in the course of time in the upper Aus- 

 tral and. perhaps, a portion of the Transition region in the vicinity 

 of its known range at that time. This would include Nebraska in 

 the West and Ohio in the East. The natural progress of most in- 

 sects introduced from Europe is westward, but there are several 



1 Numbers in parentheses refer to " Bibliography," p. 15. 



