104 FIRST ANNUAL REPORT OF 



stance the larvas of both the true and the bogus species occurred in 

 company. Thus it appears to inhabit at least five southerly regions, 

 namely South Illinois, Missouri, Kentucky, Georgia and Alabama. 



The true Colorado Potato-beetle as has been already stated, only 

 immigrated into Illinois in 1864, and in its native home, the Rocky 

 Mountains, feeds naturally upon another wild species of potato, which 

 is quite distinct from the horse-nettle, and is peculiar to the Rocky 

 Mountain region. Again, the former species has never yet been 

 known to attack the cultivated potato, and in all likelihood never will 

 do so ; for, as it has existed in all likelihood never will do so ; for, as 

 it has existed in Illinois, for at least 14 years, and in Georgia for at 

 least 44 years, without ever having been known to attack this plant, 

 which has been growing all that time in these two States, it is not at 

 all probable that it will do so at any future time. The latter species, 

 on the other hand, acquired this habit, as was shown before, in the 

 region of the Rocky Mountains, when for the first time the potato was 

 introduced there, some twenty years ago; and from that region the 

 potato-feeding race of this insect has since been spreading further 

 and further every year towards the east. Finally the bogus Colorado 

 Potato-beetle is more peculiarly a southern species, occurring in the 

 more southerly portion of Illinois, and in Missouri, Kentucky, Georgia, 

 and probably Alabama,while the true ColoradoPotato-beetle is original- 

 ly an Alpine species, its native home being the canons (kanyons) of the 

 Rocky Mountains, and it therefore thrives best and spreads fastest in 

 the more northerly regions, such as Nebraska, Iowa, Minnesota, Wis- 

 consin and North Illinois ; while in South Illinois, Missouri, and Kan- 

 sas, it neither thrives so well nor spreads so rapidly. 



The question whether the true ColoradoPotato-beetle has existed 

 for an indefinitely long time in the country that lies to the east of the 

 Mississippi river, or whether it is not the bogus Colorado Potato- 

 beetle that has there been mistaken for it, while the true Colorado 

 Potato-beetle has in reality immigrated into that country irom the 

 Rocky Mountain region within the last four or five years, may seem to 

 some of merely theoretical interest. It is, however, of great practi- 

 cal importance. On the first supposition it is not probable that this 

 bitter enemy of the potato will travel onwards and onwards towards 

 the Atlantic ; on the second supposition it will most likely traverse 

 Ohio within a year or two, spread like a devouring flame through the 

 great potato-growing State of Michigan, and finally pass eastwards 

 into Pennsylvania, New York, and New England. I shall, therefore, 

 briefly point out the minute but invariable characters which distin- 

 guish them both in the larva and perfect beetle states. 



I had an excellent opportunity of comparing the larvas of juncta 

 with those of iO-lineata, from alcoholic specimens which were kindly 

 sent to Mr. Walsh by Mrs. H. 0. Freeman, of Cobden, Illinois, and 

 .from numerous living specimens which I found around St. Louis. 



At Figure 46, the true ColoradoPotato-beetle is represented in all 



